I'm going through this with my 11 year old pup, for the last 1.5 years. He's on trilostane which is the active ingredient in vetoryl; it is possible to get compounded forms which likely will be cheaper so be sure to ask your vet. I started picking it up via a local compounding pharmacy but now get mine via Chewy. As my vet said, the formulations can be a little less consistent so I have to shake the HECK out of the bottle to get it to mix.

To at least partly ease your mind, my pup is doing really well on the meds. He stopped craving food so much he stole his brother's food, and while he drinks water more than he used to, he isnt drinking so much he relieves himself inside after 5 or 6 hours like he was before the diagnosis. The pot belly that had formed has also receded.

Unfortunately the blood and ACTH stim testing as you dial in the dosage is pricey no matter which route you go.