Caroline herself just sells, despite her poor results lately Caro is still earning more money from sponsors than anyone else, except Serena, Sharapova or Li. Caro being number 1 with their racket for months is the best thing that has happened to Yonex in a long while, that exposure was well worth the money.
This doesn't show a lot though. It shows that Caro once was a top player, your endorsements peak always comes after your performance peak, because you keep signing more and more contracts. It's why Federer makes the most off the court in 2012 he's ever done, despite obviously being nowhere near his peak in terms of results. Caro doesn't have the long lasting brand of Federer though, so unless Caro's results improve, her endorsements are gradually going to decline over the coming years, you can already see it with few companies currently rushing to her doorstep (especially global companies), they will move on to someone else, companies like Turkish Airlines dropping her from their adverts etc.
The other point could easily be argued the other way. They bought Caroline (so to speak) when she was world number 1, less than 2 years later she was dropping out of the top 10, and is currently on the fringes of the top 10. That isn't a great sell for your brand. I don't really see Yonex's adventure with Caroline as a success for them, they bought a 20 year old world number 1, they got about 5 months of good results, then 2 years of very average ones. They have to have been expecting a longer term return than that. At the end of her tenure they've had journalists, TV channels saying Caroline is trying a racket of another brand because she doesn't think she's getting enough out of her current racket, that is terrible for Yonex's brand and image, their brand player effectively said their rackets aren't good enough.
Unless you've seen the contract, you dont know what it is.
Most of these contracts are tied to performance. If she does so & so she makes this much more.
I cant believe Caroline was hitting many incentives and she didnt want to play anymore with a Yonex. That was obvious, so this was going to happen. Both Caroline & Yonex will survive.
It's blindingly obvious it wasn't value for money though. It was signed in the fall of 2010 when Caro was at the peak of her powers, she was world number 1. The only performance base contracts to an extent, the players managers/agents want the contract as protective and as good as possible, so a large guaranteed income. They also do staggered performance, so eg. I reach top 10 my guarantee goes up to x amount, and staying their gets x bonus, but the overall guarantee goes up (and for world number 1, winning a grand slam etc.). Caro's will be slightly different because it was signed at the peak of her powers, she was world number 1, she was 20 years old, they thought they were on to a goldmine, the guarantee is obviously going to be huge. Unless Yonex have released her on breach of contract or the like, if it was mutual, clearly they didn't think they were getting value for money, otherwise they wouldn't let her go (Caro can't leave Yonex unless they allow her to leave full stop).