Funny, I just posted same thing yesterday in a rat facebook group! I'm going through something fairly similar--got males because I was told they are sweet and cuddly, and of my two one is very sweet (but not so much cuddly) and the other is developing hormonal aggression. I love them all the same, but not what I was expecting.
On my post, I did get a bunch of people saying they had it done for as a little as $30-$100, and it seemed like they had legitimate vets. There were also people saying some vets charge $400+ where they live. From what I could tell from the responses, it really just seems to depend on where you live and who your vet is/what they decide to charge. So far, the only vet that has responded to me (that sees rats) said they charge $250. I am still waiting for other responses, so I will update if they are anything drastically different.
Two people also suggested looking for a local spay/neuter clinic or a humane society. Personally I feel like they wouldn't have much experience with rats, but it wouldn't hurt to ask.
Also last thing, like SQ said it seems neutering should only be done if there is a problem rather than preemptively. Hopefully both boys won't need it! Good luck!