I read it as they have a buy-back clause for the first 3 years, as in an agreed fee, not just what we paid. Then it's first refusal, i.e. if we sell they have first dibs but it's not a set amount anymore, so they'd have to match any other offers.
So basically, happy days. If he's that good that they want him back he will have been awesome and we'll make profit - as many others have said.
Welcome! Very exciting signing.