A good condition first gen RX7 with a running motor goes for about $1000. That's for one in good tune.
An RX7 with no motor(they are very easy to find, in junkyards across the world), go for anywhere from $50-$500, depending on modifications and options. You could pick up an RX7 with leather seats, air conditioning, power everything, nice wheels for about $1500, if the engine is perfect. Look on Ebay, they are always going for cheap there.
The stock first gen RX7 isn't the best looking car, it's a pretty sad ripoff of the Porsche 924. However, the 81-85 cars have a nice rear end, and there are any number of non offensive/ricey body kits available for them. All the parts except for engine parts are cheap, and available at the Mazda dealership. A complete coilover suspension kit with sway bars should cost around $1000-$1500...
http://www.erebunicorp.com/ge/mazrx779.htm
The 357 and 361 kits are quite nice, I am planning on getting the 361 if I put my 400M in an RX7. Whether I do it or not depends on whether I get a Porsche 931 for free or not...