Hello, and welcome!
I'm so sorry to hear that your cat is having recurring blockages. This is a medical emergency, and he must be seen by a vet immediately, to be catheterized and empty his bladder, or this could be fatal. In addition, he's very uncomfortable.
Unfortunately, because urethral blockages can be recurring in some male cats, they must have the perineal urethrostomy (PU) surgery, so the blockages can't recur. This will not prevent them from getting UTI's or bladder stones, if they're prone to them, but it will prevent future blockages.
The cost of the surgery varies greatly on your location and the particular vet, so your best bet would be to ask around of all the well recommended local vets, what their fees are.
I would never recommend putting down a healthy cat if he has a condition which can be fixed. I know it has cost you a lot so far, and the surgery is not inexpensive, but perhaps these ideas will help:
You might consider applying for Care Credit which is accepted by most vet offices:
This is a list of organizations that might help pay for vet visits, surgery and medication:
The most important thing right now, is to get your cat to an ER vet center, if your vet is not open, and have this blockage alleviated right away.
I hope all will be well with your kitty and please let me know how he's doing.