I agree, you can get really good value out of offering to clubs. It's also nice because it forces clubs to bid now, getting you money fastest, rather than you waiting for them to bid.
Kuyt has a faily good CA in the game, I believe, because when I played with Inter a few save games back the scouts were coming back to me as him being a good signing, on the same level as Milito. Therefore, not as surprised as you at getting that amount; in fact, I think you should have been able to get more. AI doesn't sell him for under 20 mil.