I think for most people, it's more of a psychological thing. Once you pass a certain token count, it's like you're already fully committed and don't want to get nothing for the tokens you've spent so far. Of course, both people lose out when it gets ridiculous like that.

Most I've spent was 29 tokens on a 5* 19 y/o 29 quality DL/DC/DR.. That player is now a 7* at 42 quality. So I'd say it was a good purchase for me.