I just went through the process of getting quotes from developers for a quick & fun game I am creating as well and I would say $20k sounds high but of course this depends on what you are trying to do.
I would get on
oDesk or a similar site and definitely get at least 5-10 quotes before engaging anyone for that amount. Big question you have is can you develop abroad or do you absolutely want to stay local. This is going to affect your costs substantially. When I asked for quotes for my game I was given a ridiculously wide range. The reason for this is many developers if they smell blood in the water will quote you a high price either because they can get away with it. What also happens is that some developers don't know what they are doing so it will take them forever to learn how to create your game so they give you a high quote. Don't be afraid to ask for previous proof of work and ask them for an execution plan.
If you are looking for tips on how to find the right developer visit my blog
here where I am documenting my experience.
