I am not sure if this has been mentioned as an exploit/glitch yet, but in Riverwood, you have that elven dude that can train for archery as well as be a companion. You can train with him 5 times/level. Anyway, train with him and then while the menu is still up, you can offer to switch gear around and just get all your gold back. If one were to want to power level archery, it would be very easy to do that. But then, that could already be mentioned here.ETA he needs to be your traveling buddy for it to work, as far as I can see.