I agree. I didn't say five. I gave an example of two. Two $150,000 players, a bunch of $100,000 players and a great bench is easily affordable in the top leagues. I don't train to gain money but what a lot of people do is train three players but once the training is finished sell one or two and keep the best one or two. So your training is to create your own great player and the profit from the other players is just gravy.
You also don't seem to acknowledge that the $150,000 player you have been training was probably only paid $100,000 over the least season in effect giving you $50,000 of free talent at the business end of the season. Then if you sell him at the start of the new season you have has a guy who performed like a $150,000 player for the playoffs, who you paid $100,000 a week and now having paid his $150,000 wage once you can sell him for a fortune (if young and properly trained).
I would assume that most good trainers would do the final blasting of the primaries in the last season of training and it is easy to make the salaries explode.
A PF with wondrous JS, IS, ID and RE and strong in everything else has a salary of $104,000. Get him just six pops in his last season of training, two in each inside skill and his salary explodes to $198,000. Would it be nice to have a $198,000 PF in the finals who you are paying $104,000?