I wouldn't be too interested in money either if I knew that I was gonna be a multi-millionaire before my 20th birthday, I mean the lad is still on 130k a week.Got to be emphasised its £25m and more importantly where he thought it best to develop. He had (could have had) his pick of club and chose Dortmund due to the fact it was next step in his progression. He chose Red Bull originally over super clubs / leagues as he wanted a fairly easy league, CL and "guaranteed game time" which he thought would be the best for his development as a player - Dortmund to me seems the next step on all of these.
He doesnt seem to be interested in money or prestige of the league just yet.