you can do your own math. Level 41, he is at least 46 points away from level 45 (5*). That means, W/O power training at best, he'll be just getting there at season's end. Next season you'll start again from low 4* and hopefully he'll be back at 5* at season's end, if you play him a lot, and same for the 3rd season. There onwards, forget, he'll never be back at 5* W/O power trainning.

Let's say you can buy now a high 5* player for, let's say 5 tokens. Most likely he'll be 6* or just, by season's end.
Next season you'll have a 5* player for all season. next season you buy another high 5* for more 10 tokens (you had to work ahrd on this one), so third season, you have another 5* player for same spot, and with some luck, he'll do you the following season also with 5 star. So you have a 5* player for a full 4 seasons spending less than the youth's cost.