I'll speak in the name of the Manon.
You all forget that every manager may train during a scrimmage/cup games/league games forfeited due to cup and the minutes. That's 1 (or 2, if you're training 1v1 or JS, that's the very popular option) training spots achieveable without a lot of sacrifices. Everyone may use them to make some money on training.
I would also like to notice that GM-Manon used quite low potential players. I believe that the net gain from training increases with a potential of trained player - potential works here like a multiplier of player value. I've observed some HoFs last season, and I'm convinced that you may easily achieve 700-800k$ increase of value every season. My PAS, bought by 1k as 18yo, could be sold right now for 1,75kk-2kk after 4 seasons of training with level 4 trainer. With another PAS drafted at the same time, I can say that I've gained on both of them approximately 3kk$ of value. And trust me, they haven't given me many defeats. They didn't need high level training. I managed to train them and fight for promotion to 2nd division at the same time.
You can argue that Knecht may make a much more money by tanking in DI. That's true, but we should remember - 80% of BB-managers are DIII/DIV players from macronations - 750k$ gain per season may strongly increase their overall gain and let their teams develop much quicker. I've seen many teams in my previous league, which managed to promote mainly because they've trained and saved a lot of money through this way. Therefore I believe, that training is much more important than you say it is.
Leniwy, stary, wyliniały kocur. Czasem jeszcze zerknie na polskie tłumaczenia.