Technical ability aside, parts are definitely pricier and maintenance is/ should be on the higher end of the list nowadays considering the age of these and potentially previous owner(s) neglecting it (let's face it, the majority of rx7 owners are not the original owners and finding one with the original owner selling is pretty difficult).
I've had a blown up 13b sitting on an engine stand for the past 2 1/2 years that I've been poking around in my spare time and hunting down cheap parts for from as far as japan and australia as they come up on fleabay and forums.
Definitely one of my back burner projects considering I kept it around on the whim after pulling it out of a FD headed to the junkyard which I swapped an orphaned project 2jz into I picked up cheap. Not to mention, I still have the beaten exterior to work on before that.