Right now the tokken prices to get increase a players stars is ridicilous. It's understable for high star players.
But if you want your 2 star player to be a 5star player it costs way to much. It would be alot more enjoyable if it was way cheaper. it would make your last seasons/older players last longer in your main line up. There's also 0point to use it right now your usally better of buying a new player. Would be nice to have this feature get used more often.