I think it's running at your level. It's about maximum enthusiasm. I did 72 track days in my E46 M3 in two years. I bought the car as a one year old CPO and it cost $42,000. Was that grassroots? Probably not, but I was out there every week, burning my fingers off changing brake pads at the track, smudging up my rich nappa leather by toting around Pilot Sport Cups in the back seat...
Now my budget has changed a bit and I have my LS2 GTO. I am so upside down in this car I couldn't get out of it if I wanted to. But I bought it new, I absolutely love it, and I am happy to come in near the bottom of my autocross class in it because it's so much fun to drive. Grassroots? Eh, maybe. It's my "real car" and I bring it out to events.
Now my toy cars... The '01 P71. Certainly grassroots. Cheap, easy to modify, rewarding to drive, cult following.
'93 Roadmaster wagon: I don't know if it's grassroots but it is certainly cheap. Maybe it will be a grassroots project if I decide to set my target at the Impala SS and start modifying it, but now it's just the winter beater.
'86 Volvo 745t: Sure, I'll go grassroots on this. $5 on an eBay manual boost controller and you can turn up the fun with the twist of a knob. I prefer it to the E30s and other older German cars I've had. But I haven't taken this one out to any events and I just enjoy tweaking it and driving it. Grassroots? Sure.
I would love to have new cars. I would love to have a CTS-V that I drive every day and a ZR-1 or a GT3 to take to the track. I can't do that. Per wrote a Busted Knuckles a while back about Drivers and Fabricators. I am a Driver. For the most part, the only reason I have cars I work on and repair and tweak are because I can't afford cars that I wouldn't need to do this for.
Car projects with an eye on the budget... Little compromises of performance over comfort... Waking up at 4:30 in the morning, loading up a car, and heading out in the dark to a strange parking lot for a 280 seconds of driving... Commuting in a project car and keeping a vigilant eye on the temp gauge hoping that the StopLeak holds... Changing a water pump in the parking lot at work because it blew on the way home and not even considering having it towed somewhere for somebody else to fix...
These things are grassroots. I don't care if it's a 23 year old Volvo station wagon or a tracked-out S2000. I think grassroots is all about having fun with what you have and not being an shiny happy person to people who have to enjoy less expensive toys.