I also having a hearing problem. I have total loss in my left ear, and my right ear is near normal. But, the combination makes background noise of any sort difficult for me to hear, especially what's traveling through a scope.
I start NS in a week, so I started trying out scopes ahead of time. I tried the Littman Classic SE II from the local scrub store. I had to take it home where it was quiet, but I still had trouble hearing through. So I returned it, and ordered a Littman 3000 electronic scope. It arrived yesterday, and it is phenominal! I can easily hear everything I need to hear.
You're right...good scopes can be expensive. If you get one, chain it to your waist!
Also, Littman has a 14 day free loaner 3000 if you wish to try it without buying it. Call (800) 413-1795 to arrange it.