Ask Daniel Levy. He wouldn't of negotiated a deal like this unless he thought it was a very good business proposition.
Oh, and we benefit like this;
1) We get a lot more attention from the general football populace for being affiliated with a football giant.
2) From the official statement, it will look like our players and theirs will participate in shared training/playing at each clubs' facilities.
3) We get the good will of a club that has reserve players which would walk into our first team.
4) The 'All-White' brand is going to be associated more with both clubs as/if the partnership develops rather than just one.
There's a lot more reasons I could put up that this is a good deal. Honestly, unless you are a pessimist or a stubborn fool, you should see the obvious benefits of being partnered with possibly the biggest club in the largest team sport in the world.
The people that say "oh they have first dibs on our products like Bale" are too stupid to realize that they would be after him anyway. Players that attract interest from Real Madrid usually take it up regardless of their contract situation.
Realistically, who actually thinks we will keep Bale for another five years?
Unless we make the Champions League each year, it is quite nearly impossible.
I would much rather he end up in another league than have to watch him carve our team up.
And before you say "but Inter did this and that", well I would like that crystal ball because there's no guarantee whatsoever they will do what Inter are doing regarding Leandro.
The benefits far outweigh any negatives at this stage.
Not that I am saying it is massive news or anything. But to deny that it is a good move is f**king stupid.