I have an old E46 325. I got it for a reasonable price at the time, and after 2 Outbacks and a truck it was the first sporty thing I owned. I also knew nothing about BMWs at the time. Over the years I've been slowly building it up into my dream project car. I love working on it, its been my gateway into motorsports, and it makes me happy. However, there's always the nagging thought that, "Hey, at this point you could have just bought an M3". Granted, I wouldn't have learned so much about working on cars, and I think pushing the slower car around track has helped my driving skill, but dang at this point I could have an M3 on a set of nice wheels and a few basic mods.
How about you TCL, any base model cars you've dumped way too much money into?