On the third Tuesday of September 2022, I approved a purchase order that looked like a win. ABB PLCs, a pallet of bulk contactors, a batch of private label relays, and three VFDs—all at the lowest quote I'd received. I remember thinking, “This is how you do smart buying.”
By January, that order had cost us roughly $16,000 more than the original quote. And I was the reason.
I'm the purchasing lead at a 14-person controls shop. We build small panels and resell automation components to other B2B buyers. I've handled PLC and drive orders for about 8 years. In that time, I've personally made and documented 11—maybe 13—significant mistakes, totaling probably $50k in wasted budget. Could be $60k, I'd have to open the spreadsheet. The September 2022 order was the one that finally made me build a checklist.
How the disaster started
We needed to quote a small wastewater pump station for a municipal contractor. The spec called for an ABB PLC—an AC500 model—plus contactors, relays, and three VFDs. Nothing exotic. The customer's drawing was clear, and the bill of materials looked simple.
In the past, I would've gone straight to our usual distributor and called it a day. But I was trying to be more cost-conscious, so I sent the same BOM to three suppliers. That was good. The problem was how I compared them.
I compared unit prices, line by line, and picked the lowest total. The winner had the cheapest ABB PLC quote, the cheapest bulk contactor price, a tempting relay private label option, and VFDs that were about 15% below what we normally paid. The total came in 12% under the next closest quote. It felt like a win.
The moment I hit send, I felt a weird knot in my stomach. The phrase “economy contactor” kept nagging me. But I shrugged it off. I didn't relax until the pallet arrived two weeks later—and then I saw the datasheet.
What the quote didn't say
Let me be clear: the vendor didn't lie to us. I just didn't ask the right questions. I've learned to ask “what's NOT included” before “what's the price.” That day, I didn't.
1. The ABB PLC software side
The ABB PLCs themselves were fine. But the ABB PLC software environment—Automation Builder, in our case—was not something our newest engineer was fluent in. I didn't include training or setup time in the comparison.
The quote also didn't mention firmware versions. Our controls drawings said “AC500 compatible.” The delivered PLCs had an older firmware revision. We had to update them before the programming engineer could even open the project. That cost us a day.
2. The bulk contactor price trap
The bulk contactor line looked simple: 40 contactors at $9.20 each instead of what we normally paid, $14. It was the same current rating, same number of poles, same AC frame size. But it wasn't the same utilization category.
Our panels were feeding motor loads. The cheaper contactors were rated AC-1, not AC-3. Under a motor load, they can run hot and fail early. We had to pull all 40 out and reorder proper motor-rated contactors. The labor plus premium freight added $3,800.
According to IEC 60947-4-1, contactors are not interchangeable just because the current rating matches. The utilization category and coordination data matter. I knew that. I just didn't check the datasheet before comparing prices.
3. The relay private label option
Private label relays are a legitimate way to save money on a BOM. In many cases, they're made in the same factories as the brand-name parts. But “private label” is not a specification.
This quote included a private label relay with the same socket pinout as the relay we usually used. It was 40% cheaper. I didn't notice that the coil voltage was 24 V DC, while our panel drawings specified 24 V AC.
We caught it during panel testing when the relay didn't pull in. Replacing all 36 relays cost $1,700 in parts, plus two nights of overtime. If I'd read the datasheet line by line—not the summary—it would've taken two minutes to catch.
For anyone buying private label relays, ask for the product-specific test certificate under IEC 61810-1 and verify the coil ratings. Don't rely on the “same as” claim.
4. The missing VFD line items
The VFDs also looked great on paper. But the quote didn't include the optional communication cards we needed to talk to the ABB PLC over Modbus. It also didn't include the programming software for the drives.
So the “cheaper VFD” became the “VFD plus two fieldbus cards plus one software license plus whatever time it took our electricians to learn a new interface.” That's the part I now tell everyone to include in a VFD wholesale cost guide.
To put this in current terms: as of May 2026, three regional wholesalers we use quoted a typical 10 HP VFD between $850 and $2,100 before communications options. That range is wide because the options are where the hidden cost lives. Verify current pricing with your own suppliers.
Total for the comm cards and extra labor: about $4,100.
The real cost of the “cheap” order
Here's how the numbers actually landed:
- Replacement relays and overtime: roughly $2,300
- Replacing bulk contactors: roughly $3,800
- VFD comm cards, software, and engineering time: roughly $4,100
- Firmware updates and ABB PLC software setup: roughly $1,900
- Expedited shipping and re-testing after rework: roughly $4,000
That's about $16,100. On an order that was supposed to save us maybe $2,800.
In hindsight, I should have pushed back and asked for the full landed cost before committing. But with the customer deadline already on the calendar, I made the call with incomplete information.
What I check now before every ABB PLC order
I've turned that mess into a pre-order template. It's not exciting, but it's saved us from repeating the mistake. We've caught 47 potential errors with it in the past 18 months.
- Compare the complete part number, not the description. For ABB PLCs, that means checking the exact AC500 variant, firmware revision, and I/O modules. For contactors, it means verifying the AC-3/AC-4 rating, coil voltage, and auxiliary contacts.
- Ask “what's NOT included?” Communication cards, programming software, terminal blocks, mounting brackets, commissioning hours. Get them in writing before choosing a quote.
- Verify relay coil ratings and approvals. If a relay private label offer is too good to pass up, request the IEC 61810-1 test report and a sample for bench testing.
- Build your own VFD wholesale cost guide line items. Unit price is one row. Add communication modules, EMC filters if required, software, training, and supported protocols.
- Check the ABB PLC software compatibility before the project starts. Which version of Automation Builder? Which firmware does the PLC ship with? Does your engineer know that version?
- Add a 5% contingency for rework. If the quote looks too low, add the contingency and then ask yourself why the number is low in the first place.
Price is not the same as cost
The “lowest quote wins” habit comes from an era when components were more interchangeable and quotes were more complete. That's changed. Today, the margins are thin, and the hidden line items are where companies make up for a low base price.
That's why transparency matters so much to me now. The vendor who lists all the fees upfront—even if the total looks higher—usually costs less in the end. And the buyer who asks about the hidden costs first is usually the one who doesn't get burned.
I still buy from multiple sources. I still compare quotes. But now, the first question I ask is always the same: “Show me everything that isn't included in this price.” That one question has saved us more than the September 2022 order ever cost.
Pricing referenced above is from quotes we received in Q3 2022 and Q1 2024, with VFD ranges updated from May 2026 regional wholesaler quotes. Verify current ABB PLC, bulk contactor, relay, and VFD wholesale pricing with your distributors as rates change.