pbbth, my fat cat had crystals in his urine years ago, our vet told us it can quickly become fatal in males because their urethras are so small and easily blocked. He went on a prescription food (that we mix with off the shelf stuff to prevent tummy troubles) and he’s been fine ever since. I hope Joey is okay.
Pollux Oil, I keep a box on Benadryl non-drowsy pills onhand for an allergic friend. They don’t eliminate the sneezing completely, but they help. I also vaccum and dust everything before she comes over and open the windows to get some fresh air in. Of course, if you’re letting them sit in your lap none of that is going to help you 
Happened to one of mine too. And of course he had to wait until a holiday, so I had to take him to the uber-expensive emergency vet :rolleyes:. Was it struvite? I titled my little LJ post on the topic as “My cat’s penis is like the bore of a dewatering centrifuge…”, since I was used to have to chip out struvite scale blockages in wastewater treatment plants ;).
Anyway, best of luck to the little guy. Mine hasn’t had any recurrences since ( he’s been partially on a special diet since then of course ). Just like human kidney stones, proper hydration seems to be key. Mine really benefited ( I think ) by the addition of a kitty fountain, which seemed him to inspire him to drink more often. Also a larger proportion of wet food seems to be frequently recommended.
There is, but you have to get it before the animal is sick, and most pet insurance plans don’t cover a LOT of common illnesses. I never found it to be particularly worthwhile.
As for cost: that’s the cost of medical care.
First google hit for “cost ultrasound” sticks it at approx 200$ for humans. X-rays seem to be about the same; 200-300$ each. Blood and urine tests seem to be anywhere from 50 to several hundred dollars, depending on the test required. I found one site that seems to peg an over-night in a hospital at about 2400$.
We are lucky to have some sort of insurance, either through our jobs or government programs, etc. But if you had to pay the bill to treat a kidney infection, you’d be just as surprised at how much it truly cost!