Sure, if the best offer was 4x4, but all you need is two GMs that want the same guy. Then it goes to 4.5x4, then 5x4, and it just keeps going. It's why the players wanted free agency, and fought against the cap. They know they're in demand, and will get stupid money if given the opportunity.
If GMs tied up all their cap space in young guys, eventually the 27+ UFA's would start getting less, but then teams end up using their leverage in the lack of RFA movement to get the 21 year old at a discount. They have to spend X amount though, and might not have a young player that commands huge money, so when the 27+ year old guy comes around, he gets the money because GMs are desperate for any talent.
There's no perfect solution. I guess the least complicated one is get rid of the cap, and if any teams can't survive the free market, then they just need to go. Fewer jobs for players, but oh well.