Trade-in maximum offer calculator
Start from what you expect to sell the vehicle for, take away what it will cost to get it ready and carry it, and take away the profit you want. What is left is the most you can pay for it.
How it works
Most you can pay = expected retail price, minus reconditioning, minus other costs, minus the profit you want, minus the holding cost for the days you expect to hold it.
The expected retail price is the number that matters most, and it is a guess until the vehicle sells. Check it against what similar units are actually selling for, not what they are listed at.
Using it at the appraisal
Run it with a cautious retail price and a realistic recon figure. If the customer wants more than the result, you can show them the working. Tax treatment of a trade-in depends on the province, so work that out on the deal, not here.