I know that's something my vet always notes; Bud's mood when he's there.
I remember the unsureness I felt when I first found him; should I feed him at all, if that would just add to his discomfort? Or was he hungry? He just couldn't tell me, and it was so frustrating.
Okay, I found it. Here are the charges from Bud's first vet visit at the Greater Annapolis Veterinary Hospital. It's an emergency clinic, so by no means are they iguana experts- they just did the best they could.
Exotic Animal Vet Fee- 46.00
X-Ray: Two Views- 80.19
***ENEMA- SOAPY #1***- 31.11
Calcium Gluconate Injection- 19.50
Chronulac Syrup (Stool Softener)- 5.65
I include the other stuff because if you're dealing with a situation like mine, (constipation, paralysis, mysterious history, possible MBD) he might need the same treatments, and you might be interested in what others charge.
Why did these vets say there is "no hope"? My feeling is that as long as the iguana is interested in his surroundings, shows definate signs of promise (pooping a few times by himself, walking around and tongue-flicking), there is worth in trying to save him. Apathetic and listless iguanas are likely feeling pain, from my small experience and reading what others write.
This is from Anapsid.org:
"If the blockage is due to heavy parasite infestation, a clump of ingested human or pet hair, or larger pieces or clumps of substrate (or other foreign objects), then the bathing or increased heat will have little to no effect and the iguana must be seen by a vet for further diagnostic work-up and treatment.
Severe metabolic bone disease and paralysis may also lead to constipation. Again, a vet visit and work-up will be required to determine the cause and initiate treatment."
Did your vet give you a specific reason there was "little hope"?
If it was a clump of hair or some other obstruction, why was he able to poop once before? Maybe it's a result of the MBD, and focusing on that underlying cause will help? I don't know.
I'm sure you've heard this so many times, but- find another vet.
Others have written this before, so I'm just repeating it- a vet who knows a lot about reptiles isn't necessarily better than a vet you trust. I did have some luck with a general vet, before I found the one I go to now.
I know your situation is more dire, but about the pooping, don't give up hope. I went on vacation for five days a few weeks ago and left Bud in the hands of a capable petsitter. He ate and behaved well while I was gone... But it has taken me three weeks to get him to poop normally again. He didn't poop at all for four days when I got back, although he was eating (a little). After that it was sporatic at best.
I couldn't find any pictures of iguana poop, and my computer won't open the article called "Feces and Urates" on anapsid.org for some reason. It's under Information Clusters- Green Iguanas- Health- Feces and Urates. It has a really good description. I guess the best way to describe healthy feces is: not smelly (smells kind of like wet soil and vegetables), dark brown, like the color of topsoil, tapered cylandrical shape, and they come out after the urates, which look a lot like egg white, but a little bit yellow.
I don't know what else to say but that I know the feeling of having been struck over the head with love for an ig that just fell into my life. At times I have thought that I have put so much work into him, that he'd BETTER not have the nerve to die. Keep working the sun magic, maybe find vet #3, and let us know is all I can say. 
-Erin
