Insurance on these cars would cost a small fortune as well, as would replacing the tires, also maintenance because it has that special, not a v6 or inline-6, but flat 6 engine design, so gotta go to a special shop.
Tires more expensive? Yes, because they're bigger. ~$1500/set versus $1000/set (shipped, mounted and balanced) for the Miata, and the rears wear out about twice as fast.
Maintenance? If I went to a dealer for service, labor rate is 24% higher compared to a local Mazda dealer. I instead go to one of the best Porsche independents in the US and he's about 12% more than a local Mazda dealership, and he has way cooler stuff in his garage (last time I went, three 959s, a one-of-17 TechArt CTR3, and other craziness). Though still lots I can do myself.
Parts? I did a full brake job recently, and it cost ~10% more than something like a Subaru WRX STi. I actually used uprated brake fluid (which was +$20 over OEM), though everything else was OEM.
The only major long-term expense is engine rebuilds. Figure 25-30% more than rebuilding a mainstream V8 like a Toyota 1UR/3UR, Ford Coyote or Chevy small block. Though that's usually every 15-25 years (depending on engine hours at high RPM), so that's something you just sock money away for well in advance.
Janky Mustang GTs are everywhere
The act of stealing them may not be easier, but the enterprise of stealing them is.
Vipers aren’t exactly in the same group. It’s not performance based, just statistics.