Stretching it there a bit I think, it's an aid, ultimately the price at which you buy back, though discounted, could still be huge and is dictated by the market/performance.Thing is; as I already noted, a sell on also acts as a buy-back by proxy anyway......
Insert a first-refusal and it's even more solid.
eg 15m +25% sell on >>>>>>> Eventually CP sell for 40m... We get 10m and Palace still double their money..... Or we can buy back at 30m and Palace are still doubling their outlay.... Palace get 30m upon sale either way.
Whereas a buyback is a price dictated by us in the sale agreement. If you have a buyback set for £10m and the player goes away and turns into Gareth Bale re-incarnate, then you can buy back a player worth £100m for £10m, if you've just got a sell on then sure you can knock 20% off but you'd still be shelling out £80m.
It doesn't matter all that much anyway, I'm just a wannabe perfectionist when it comes to our dealings, both in and out.