This is, unfortunately, part of the hobby. We’re going on some 50 years of IBD now.
There was an antibody test for IBD developed some 5 years ago, iirc, at the University of Florida (which already got a mention). IBD (thankfully) does not survive for long outside of a carrier. As the hobby got better about mites, ticks, and (by proxy) food item sourcing/freezing the IBD transmissions went down. Snakes, including pythons, can carry IBD. Pythons don’t last long.
Nidovirus is much heartier outside of the body but there are also tests for that. Adenoviruses is a family and not a single virus. There isn’t just one test and usually the disease is diagnosed by symptoms-only, afaik.
Generally snakes are housed alone without bedding or other items shared and most keepers are using home grown or frozen food stock instead of externally sourced live. General sanitary measures (hand sanitizer, washing between handling, etc) have improved, as well. An entire collection crashing is possible but you don’t hear about it happening nearly as often as a couple of decades ago.
One of the things that always drives up the cost of these tests is the lack of people committed to getting them done. There are enough reptile owners today to boost reptile care across the industry tremendously… but the average person will tell you horror stories from 20 years ago. Even worse, there’s a current YouTube celebrity pushing that reptile veterinary medicine is useless trash… and that’s why you should send them unhealthy animals to resell. I’ve had my share of vets look at the vent of an animal for $200, which is a huge waste of everyone’s time, but that doesn’t mean there are not qualified individuals out there.
I believe Brian Kusko has a video where he performs the nidovirus sampling from a kit on one of his snakes. I can’t say if that suggests Freedom Breeder actively tests but he might be worth reaching out to if you’re really interested. Other breeders like Kevin McCurley have released information, as well.
ARAV has a directory of veterinarians you could try to locate and speak to for more information. The directory is kind of outdated and not inclusive of all of the vets in an area, in my experience. Still worth a visit if you want to try to find a local vet.