You should be able to get $300 for the complete dash if you're a nice guy & include the glove box, knee panel thing and the rectangular filler plates that go all over the sides.
Seats can range anywhere from $100 to $500 depending on the condition of the material as well as the desperation of the buyer and/or seller.
Floor mats, well...varies a ton on condition, just like the carpet. You might get an offer of $20 or $100 depending. There's a set I've seen on eBay recently at something like $500...and it drops every couple of months. heh...
Complete carpet can go for $50-$200 depending.
Some folks have gotten complete LE interiors for $500-$700 from places like Planet Miata.
If you happen to have a tonneau (full cabin cover, not the top boot, mind you) in the LE red, those can range from $200-$300. Having all of the dash & mirror hardware can help a lot! The top boot can go for up to $200 if the buyer wants it bad enough.
There's plenty of other stuff, like the Bilsteins ($50-$200 depending on condition & how bad you want 'em gone), front & rear chin spoilers (front's still under $200 new, so maybe $130-150. $150-200 for the rear as it's discontinued), rear deck spoiler ($150-200) that will find an easy market if you're fair with the prices.
Hope that's a bit useful. Oh, and how much do you want for the glove box & knee panel thingy? heh...