If he didn't sign with giants like Nike and Adidas (and instead Uniqlo), maybe it's not money he's after. I think he's after something that's unique his. Originality and notoriety is what he wants: something no other player has, and he wants a company that can deliver it to as many customers and fans as possible.
Sergio Tachini was fairly unique but lacked the ability to deliver product supply to the masses. He dropped them.
The Head Speed series are his, in the way Federer has the Tour 90's, Nadal somewhat has the AeroPro, and Sampras had the 88.