Raze...
To prevent a one time slaughter of all the dogs (assuming no attempt was made to protect them by those responsible for a racing ban), you are willing to accept an annual slaughter of most of them?
To prevent the near-total slaughter of every single racing dog, including all the puppies at the breeding places, I am certainly prepared to accept an annual cull, provided it is carried out humanely.
Maybe it would be better your way - the indiscriminate slaughter of 99% or more of them - but somehow I do not feel that would be the case, nor would it actually address the problem.
If you close down dog racing because of the cruelty of the humans who run the races, all they do is go underground. Dog racing becomes another sport held in secret and the animals are tortured and destroyed in greater numbers than ever. As you've said, there is money in it - and where there is money, there are always people willing to break the law.
Moreover, it is a popular sport and one that it would actually be far easier to clean up than to actively ban. The sport itself is not like bull fighting - the deliberate torture of an animal for the amusement of crowds. Properly regulated and with appropriate penalties for animal cruelty, there is no reason whatsoever to ban the actual races.
The races itself are not the problem, and they never have been. It is the behaviour of the humans that run them in certain parts of the world that needs changing.
Greyhound racing is quite popular in Britain, but any dog handler who behaved in the manner Gal describes in this country would be in jail so fast their toes would not touch the ground.