The value on the trade market depends on a GM perception. If an GM think Chiarot was the missing link to put their team to the top then he will give a lot to acquire Chiarot.
While what you say is true in many situations, you can not ignore the overall environment.
GMs overpay when,
1.) They think the acquisition of one player is going to make their team elite
And
2.) The options are extremely limited.
I don't believe any GM in the league is saying "Chiarot is the guy that makes us a champion".
And there's likely going to be 10-12 teams looking to sell players this deadline, which will greatly expand options and lower costs.
When I look at the trade environment, I see 12 teams that are sellers, they won't be buying ufas.
Then there will be 10 bubble teams. I just don't see any bubble teams trading their first for Chiarot.
Then we have the contenders. 10 teams that may legitimately be looking to add a guy like Chiarot, but 4 of them have already traded their 1sts in previous deal and are unlikely to sacrifice back to back first rounders for a Chiarot rental.
Lastly, there is likely going to be several decent players on the block this year, more than usual, which is going to dictate the market and perception for GMs and their actions.
Ultimately you are right in that it only takes one GM with a misguided sense of value for a given player, but when there are less GMs in the market and more options for those GMs, the likelyhood of selling a player for premium assets is greatly decreased.