Oh my, did he ever have Gout!!! I'm sorry that first vet didn't know what he was doing, I was pretty sure he had Gout the first time I read your post and saw his photos, it's unfortunately not uncommon for vets to not have a clue about Gout in Dragons unless they are very experienced Reptile Vets. He's most likely in a lot of pain and that's why he's not eating, Gout is extremely painful and it's very common for them to stop eating completely, in fact it happens almost always because of the pain. Did this Reptile Vet mention a prescription pain medication/swelling medication for him? That's something you want to call and discuss with your vet, tell her that he has stopped eating and is not moving around much, she may prescribe him some Metacam or better is Tramadol.
You may have to start force-feeding him by using an Oral Syringe, but if he likes the Baby Food then definitely mix the Alfalfa meal into it, as already mentioned it contains a form of protein that will not make the Gout worse like the live insects will. I would definitely follow Danielle's advice and order some live Silkworms on Amazon for him, the Serrapeptase is a natural pain reliever and takes the swelling down, and they are one of the best live feeder insects for Dragons anyway, plus they contain a lot of Serrapeptase naturally in the inside lining of their GI tracts, so they tend to help a lot with the pain and swelling in conjunction with the Tart Cherry Juice/Extract...I actually found a tablet form of "Tart Cherry Extract" at Walmart the other day by accident while I was looking for something else, you get a bottle of 100 tablets of Tart Cherry Extract for $6, it's Spring Valley brand in a green bottle with a yellow label and is in with the human vitamins and supplements alphabetically in the Spring Valley bottles under "Tart Cherry". It's probably a stronger dose than the Black Cherry Juice you're giving him, and you can dissolve the tablets into either Unflavored Pedialyte or even the Cherry Pedialyte (I buy the generic Walmart brand of Pedialyte, much cheaper). It's extremely important to keep him extremely well
hydrated with fluids and electrolytes, this will keep his kidneys flushed out and help to get his Uric Acid Levels down, which are pretty high. So that's why the Pedialyte/generic equivalent is better than just giving him water. He must get his
hydration through his mouth, soaking him in water or anything else will not
hydrate him unless he drinks the water through his mouth, so I'd be offering him the Pedialyte several times a day, throughout the day using an eyedropper to drip water on his snout, or even by force-feeding him the fluids. The BSFL you bought are also a great live feeder insect (Phoenix Worms, same thing), I've been feeding them as my primary live feeder insect for years and never had an issue, so keep trying to give them to him, and always give him the darkest colored ones first, as they are the closest to changing over to beetles, and they also contain the highest calcium content...
You can also buy Alfalfa Meal and Alfalfa Pellets that you can easily crush into powder at any Tractor Supply, they are extremely inexpensive at Tractor Supply, and they sell large bags of them to feed both horses, cattle, and rabbits. Just make sure that they are not the medicated Alfalfa pellets, as they do also sell special, small bags of Alfalfa pellets that are medicated with antiparasitic medications. But just in case you need to buy more, they have large bags of plain Alfalfa pellets/meal very inexpensive.
As far as the Allopurinol, I'm so, so sorry that your vet did that to you!!! Allopurinol is one of the cheapest prescription drugs there are, they cost the same as a simple antibiotic does from a human pharmacy without insurance. Your vet sold you the exact same human grade prescription Allopurinol that people would get from their pharmacies for Gout and other health issues, the reason the vet's prescription is so expensive is that they either order it already dosed for a dragon's weight, or the vet does it herself, but either way she really, really ripped you off, and that's awful. I mean that's probably the worst rip-off by a vet I've seen in a long time, as Danielle said they do not make some "special veterinary formulation" of Allopurinol, it's all coming from the same pharmaceutical companies that supply human pharmacies, and your vet has to know that. A month's worth of Allopurinol for him should not cost you more than $10-$15 maximum from a pharmacy, and all pharmacists mix formulations for veterinarians/animals on a daily basis, in fact the veterinary formulations are really the only prescriptions that pharmacists have to mix up by hand any more, because they prepare it from the pills that come in doses for people. I can't believe your vet charged you over $200 for 2 month's worth of Allopurinol...I'd be calling her and asking her why she didn't just call the prescription in to the pharmacy, she most likely does this every day as all vets do, all she has to do is call the prescription in to your pharmacy and tell the pharmacist the proper dosage, just like a human doctor does. The pharmacist will make the correct dosage from human pills and put it into a liquid form for you to give to him for free. That's what you paid for, the labor or the vet putting it into the correct dosage and into liquid form. That's really upsetting, that cost her no more than $20-$25. That just sucks. Again, I'd call her and tell her that several experienced people on the bearded dragon forum were horrified that you paid over $200 for what they have regularly paid no more than $20-$25 for at their own human pharmacies, and that all of them had reptile vets who called the prescriptions with the correct dosages in to their pharmacies. If she knows that you're onto her and you now know that several people have beardies with Gout and that their Certified Reptile Vets simply called in the Allopurinol prescriptions in to their human pharmacies and that they all paid no more than $25 for 2 months worth, she might feel guilty and refund your money. It's definitely worth a try at that price, you could use that money to order him Silkworms...