the noise is the issue and caponising him won't necessarily stop it entirely. So the main problem is neighbors complaining and if you spend all that money on the procedure and they still complain you'll be very annoyed.
What breed is it? The bigger the bird generally the more noise they make. I did keep a very noisy cockerel successfully for 5 years with him sleeping in a noise insulated box but I'd never do it again! Am now on the quest to find the least noisiest cockerel which will have to involve getting rid of several but having dealt with a noisy cockerel makes the process easier. I hate the process but chickens are long term, would you rather have a headache for the next 10 years or deal with a headache of getting rid of him for one day? At the time I obviously was not ready and tried dealing with the problem without killing him and eventually I managed to give him away but he most likely ended up as dinner somewhere.
Anyway if you are not ready then get some sound insulation and build a box for him. It needs to have a small tube for air but the point is to just lock him in the box every night and release him once the neighbors are up and cock won't need much air so focus on stoppng the sound - build the box bigger so it holds more air. Sound insulation is not cheap and you need the best you can get, as thick as possible. If you use 1 foot sound insulation your box can easily end up measuring 4 foot by 4 foot.
Is it worth it? Not at all lol. But I completely understand getting attached to something makes us do irrational things.
Ps: if you do opt to keep him in an insulated box (sound insulation that is which when I last checked was about $400 for the amount needed) make sure he cannot eat the insulation as he will peck his way out otherwise