The costs of eating seafood in Bangkok is largely dependent upon where you eat. If you eat in a mall, you are going to pay for it. Fortunately, in Bangkok, there are a number of outdoor venues that are not too bad. In fact, in the Ramkhanhaeng area, there is a pretty good place. Very popular. It is located directly across the Bangkok Interplace Hotel. ( I don't recommend that place except the suites. The Chinese guests smoke in the rooms.) On the surface, you probably wouldn't go here.
Costs. This is what is really interesting. You get the following items.
A type of green in oyster sauce. Not seen in the USA.
Okay, all of this was just over 1000 Baht. That is exactly 30 dollars by the current exchange rate in 2012.