It is different for every player. Normally I refuse to pay more than 5T for a player. Most I get for 2-3 Token, but a lot of dead players.
I may find 1 or 2 good ones per season. If I find the good one for the position I need a new player I stop searching. This season for example looking for DR and MC on my main account to train next season. These are the players I bought:
DR 66% for 1T - bad
MC 61% for 1T - bad
MC 54% for 5T - OK but not great, I still have him as he is my best so far
DR 70% for 3T - Also ok but not great, want to find better, also he is generally too high for me
MC 50% for 2T - bad
So 5 players bought and still not happy, I hope to find better talent for the rest of this season.