The example is made up. Brightline Painting needs 6 office laptops and has three quotes from made-up vendors. The answers come from a real ChatGPT run on October 20, 2026.
What are the most common quote comparison mistakes?
Seven mistakes cover almost everything that goes wrong:
| # | Mistake | Fix |
|---|---|---|
| 1 | No "same basis" in the request | Say units, what is included and how long |
| 2 | Picking the lowest unit price | Compare totals with setup and warranty added |
| 3 | Reading a lease as a monthly price | Turn it into a total over the term, plus any buyout |
| 4 | Letting ChatGPT fill in missing prices | Say "Do not guess prices that aren't there" |
| 5 | Not checking any total | Check one total by hand |
| 6 | Deciding before the gaps are answered | Send each vendor its open questions |
| 7 | Vendor pricing in a normal chat | Turn on Temporary chat first |
Which mistakes happen in the request?
1. No same basis. "Compare these" can give a different answer every time. The lesson's request defines it: the total cost over 3 years for all 6 laptops, with setup and a 3-year warranty included. It also names every column: vendor, laptop model, price per laptop, setup, warranty, delivery, how you pay and that total. Then it asks for the math under the table and a list of what each quote leaves out.
4. Letting ChatGPT fill in missing prices. Without a clear rule, a missing price can be filled with a plausible number. The lesson's request ends with "Use only what the emails say. Do not guess prices that aren't there." In the real run, ChatGPT wrote "Not specified" for payment terms on two quotes and delivery on the lease, instead of guessing.
7. Vendor pricing in a normal chat. Vendor pricing is business information. In the lesson you click the Temporary chat icon before you attach the file.
Why is the cheapest-looking quote often not the cheapest?
2. Picking the lowest unit price. Riverbend looked cheapest at $949 a laptop. But setup is $65 each and the 3-year warranty upgrade is $119 each. Once you add them, Riverbend's total is $6,798, more than Summit's $6,774, whose $1,129 price already included setup, file migration and a 3-year warranty.
3. Reading a lease as a monthly price. Keystone never gave a price per laptop. Its quote was $189 a month for all six on a 36-month lease, with setup and warranty included and a $1 buyout at the end. ChatGPT turned it into a total: 36 × $189 = $6,804, plus $1, is $6,805. A lease looks small because it is monthly. On the same basis, all three quotes were within $31 of each other. The estimate vs quote entry covers what a quote should commit a vendor to.
5. Not checking any total. Check one total by hand. If one is right, the method is right. The lesson has you check Riverbend: 6 × $949 = $5,694, plus 6 × $65 = $390, plus 6 × $119 = $714. Total $6,798. It matches.
What should you do before you decide?
6. Deciding before the gaps are answered. When totals are this close, the missing details decide it. ChatGPT's bottom line said so: Summit IT has the lowest stated total, but the ranking could change once tax, shipping, payment terms and any other fees are confirmed. Its "What to ask each vendor" table lists the gaps for each quote: payment terms, tax, shipping, what setup includes, what the warranty covers, delivery dates and how long the quote is valid.
Turn those gaps into an email. The lesson's follow-up to Marcus at Riverbend states the $6,798 total, asks six questions and asks for a reply by Friday, October 30. Check that nothing in it promises to buy, copy it with the copy icon and send it from your own email. Do the same for the other two vendors. Then decide on full numbers, not on how a quote was written.
Try it free, step by step
Compare Vendor Quotes Side by Side using ChatGPT. Turn three quotes written three different ways into one table on the same basis, check the 3-year totals yourself, see what each vendor left out, and send the follow-up questions. You do every step yourself in a practice copy of ChatGPT, it checks your work as you go, and “Do it for me” finishes any step you get stuck on. Free, and nothing touches your real accounts.
Start the free lessonKey takeaways
- Define the same basis: units, what is included and how long.
- Compare totals, not unit prices. Extras change the ranking.
- Turn a lease into a total over the term, plus any buyout.
- Tell ChatGPT not to guess, and check one total yourself.
- Ask each vendor what its quote left out, and get the final price in writing.
The vendor quote FAQ answers the how-to questions. For quotes you don't have yet, the Deep research vendor comparison lesson researches public vendors for you. For the difference between the two documents, read quote vs estimate.
Frequently asked questions
- Can I paste the quotes instead of attaching a file?
The lesson puts the three emails into one text file and attaches it. Either way, include the full text of each quote.
- What if ChatGPT's total doesn't match mine?
Look at the math under the table and find the line that differs. It is usually a missing extra or a different number of units.
- Should I always pick the lowest total?
Not when the totals are close. In the lesson they were within $31, so payment terms, tax, shipping and support decide it.
- Can I use the sample quotes?
Yes. Download the made-up three-laptop-quotes.txt and try the same requests in your own ChatGPT.
