I absolutely agree with u. Unless u're really really really really really desperate to train some trainees, I think advanced trainers are sufficient. When I joined this game (at the end of season 12), I thought it's good to have superior trainer (that time i had about 300k) so I kept trying to get one but it never worked because on average, superior trainer are sold for about 500k when their weekly salary is around 20~30k.
So I thought this is totally nonsense and I tried for advanced trainers and WOOOOWWWW MY LIFE!, I got 14k weekly salary advanced trainer for 5k!!! So I saved roughly 300k from buying a trainer who has one lvl below! Makes more sense to get an advanced trainer. Then I used the left over money to expand my arena and buy a decent player who's currently the best player in my team!