i guess the best way to look at it is. to get a similar power/weight ratio car to do the same things would be a s13 turbo with coilovers, and rims which would set you back 10g anyway...
mx5 is basically an AE86 without the roof and they cost 8 to 10g stock std.
spending less on a base car = more money to spend on car its self (compaired to buying a more expensive base car) jsut happens that the parts your looking for a 25 years old rather than parts that are still being made new for the S13.