There is always risk of disease, whether from a shelter kitty or a breeder: the shelter cats, because of the high exposure to other cats, and diseases they may have been exposed to before arriving. Many people have adopted healthy shelter cats or kittens. Most reputable breeders will only sell and keep healthy stock and kittens. Testimonials from previous kitten customers is a good way to find if a breeder has sold them a healthy kitten, or referrals from other breeders if they do not have what you are looking for. If you are able to visit a cattery, look at the other cats and kittens there for signs of good health, as well as the condition of the cattery. Ask what diseases they have been tested for. And of course, once you have purchased another kitty, take them within a few days to your own vet for a health check. This is required with almost every kitten contract I have seen, including mine, and is another reason why quarantine is so very important.
Most kittens will be sold as "pets". This may be because they do not meet the breed standard in some way to be shown or bred (bad coat, tail kink, smaller ears, etc) but are beautiful and healthy just they way they are

"Breeders" are usually only sold to a person who already has an established cattery, or has been mentored by another breeder for beginning their own. The higher price of breeder kittens reflects the quality of that kitten and additional fertility guarantee that comes with a breeder. If that kitten does not produce within a certain time frame, the original breeder of that cat must replace him or her....
If price is a factor to you, you could consider an older kitten/young cat or retired breeder. They are usually priced quite a bit less, and make wonderful pets

And honestly, any other breed of cat can be pricy, even more so than Savannahs.
I have seen lots of shelter kitties on Petfinder that are quite Savannah-looking (of a lower generation). Other breeds of cats can be quite high-energy, too. Bengals, Ocicats, Oriental Shorthair, Siamese, Abyssinian...are just a few. Type in any of those breeds (along with Tiger, Egyptian Mau and Tabby) on the Petfinder search. You'll be surprised at all the spotted kitties available. You could also contact specific breed rescues. I know Savannah Rescue always has a long waiting list.....but there are several Bengal rescues, and Oci....