This is also true Pat, and not to sound like a smart a$$, I have thought of most of these issues ...
1)it is our 2nd car (no 1 car is a subaru Liberty wagon) so doesn't see a lot of road kms
2)With subarus there is so much interchangability that most parts will just be late model STI parts (6 speed with DCCD, rear diff/axles, etc)
3) another impreza shell for $4k, get the mrs to drive me to work for a little while or get fit and start jogging/cycling
4)Most work should be able to be done in a weekend ( I have already done 6 speed conversion to a friends 92 subaru in 3/4 of a day) I aim to have all parts for a particular job before starting it.
5) see 1)
6)Local for us here in Australia is not that local and would cost several hundred dollars every meeting without a trailer.
3rd car in the family is then another cost but will come later.
Also you miss a big factor here, I look forward to my drive to and from work at the moment which if it were just a commuter this would be lost. Whatever car I drive I like it to be enjoyable. (even the No 1 family car is a 3.0 H6, 6 speed manual!)
I guess it comes down partly to most of motorsport on a club level doesn't make any financial sense, yes some things are smarter ways but overall there is some personal preferences in it all.