I picked my trainer during the playoffs for a tad over $500k. Every Superior Trainer (under $25k salary) I was bidding on was going for over $500k, I finally just bit the bullet since the Trainer I had had a salary that was getting ridiculous, so even spending that kind of money on a new Trainer means I'll have saved that $500k well ahead of the next All Start Game. I'm not sure when anybody else was able to land a Superior Trainer for less than $500k, but maybe I'm just a fool for overspending. The last time I had to re-up on the same sort of Trainer, it cost me about $350k (I think), but that was more than 2 seasons ago (which gives you an idea about what sort of salary the Trainer had before I just replaced him).
Don't ask what sort of Chunks they are, you probably don't want to know. Blowing Chunks since Season 4!