Tops can vary on these from $200-$500 or so for the top, but it would still have to be installed. Planet Miata has a deal where for $600-$700, depending on what type top you want, you can get a new top installed on a used frame ready to bolt on, and last I checked shipping was free. Just depends on which route someone would want to go. Used hardtops go for about $1000.
The price is very negotiable depending on if someone wants snow tires, it would be more then $2000 if someone wants the hardtop from the other car. I'm willing to be flexible, I just have to state an asking price.
Now as I just told Gabe, $700 isn't going to cut it.