In FL they will bust your azz for that. They have a program that compares stated bill of sale values with KBB and pricing sites and if you bought a car or boat worth $50k, and you say on the bill of sale that you bought it for $10k, both the seller and buyer get a nice letter from “the man” telling you that the transaction may be investigated and asking you to attest in writing under penalty of both fraud and perjury that you did indeed sell or buy it for $10k. Both parties are required to sign the letter and return it to the state. I got a buddy that almost got his butt in a pretty big sling over that 3 yrs ago. You’d better be careful about doing that and especially admitting to it on a public forum.