I'm in Chile at the moment.
Plenty of restaurants have lunch meal deals. They tend to be quite decent and cost 4-6 USD. This typically gets you a starter, a main course and, sometimes, a drink. The main course can be a fish. Almost always, this is not only great value for money, it's also a good meal.
At the Mercado Municipal in Santiago, which is famed for its sea food, but also where competition is quite strong, expect to pay 10-20 USD for a very good meal, seafood or otherwise. Plenty of these plates are meant for sharing.
One speciality is a kind of crab (king crab?), where the largest ones, at the Mercado Municipal, sell for a bit over 200 USD.
I have not seen, nor looked for, lobster.