I used to do web design but it did my head in. This is mainly because the clients never came up with the content.
In your case, you have loads of content, and the fact is photography websites have been done before - You shouldn't be paying someone to build it from scratch unless you have some requirement that doesn't fit any of the multitude of templated sites out there.
And don't balk at the mention of template sites - most of them can look nothing like the template when you've finished messing around with the design.
I have often almost fallen over when told how much people pay for websites. Sure, you are paying trained/educated people but seriously.. Websites are like diamonds - We pay so much because we EXPECT TO pay so much. The reality can be something different.
I would say that 70% error is a BIG error in an estimate. I paid someone $400 once to do a panel job that he quoted at $200. To me, that is a 100% f*ck-up. I also found out the guy used cheap materials.
If I was you, I'd set apart some time to demo some of the photo gallery sites that are out there. Believe me, there are a LOT of them.
I have used one solution in the past called quickCart and I like it. It has everything you want. There is a free version and paid versions, depending on your requirements:
http://opensolution.org/quick.cart,en,9.html
Demo is here:
http://opensolution.org/Quick.Cart/demo/?sLang=en
With any site that has user-managed content, you will have a learning curve, but it's not that hard and if you don't feel up to customising it, find a smart 12-year-old to do it for you
I know you already have money invested, but if you come to the conclusion to begin again, try this solution.
I think it really is that good, because it keeps things simple, and who wants to spend all day in front of the computer? (HANDS DOWN YOU LOT!). (And it's built with PHP, the way good websites are).
(Oh, and I have no affiliation with opensolution.org, I just really like the product for what it does).
I hope that helps. Please don't pay thousands!