Why count? It's not like you NEED to upgrade, and unless a part snaps in half, it's usually fixable for a smaller cost, if you learn how to do it. Just watch wear, and replace parts as needed.
I did some quick math the other day.........I bought a Dakar Expert back in 2000, shop owner's girlfriend bought the Pro. She wanted my drivetrain and disk brakes, and I liked hers better, so we swapped. Shop owner did the math, I wound up saving a couple of hundred. When I did go disk, he had me watch the shop while he went on a riding vacation for a week. He built my disk wheelset as payment, threw in a full set of Flak Jackets, and half the cost of my front brake. Rear brake I got from Avid for nothing. One lever got a little sloppy, so I got another pair, also free, and kept the wobbly set as spares. Still have them, just in case. Found a bad weld on the BB shell after two years, had Jamis warranty the FS frame and send me a Komodo hardtail instead. Sold the rear shock, made some money on that. I figure I wound up with a bike that would have cost me $1600 if I'd done it all just buying in shops for about $700 or so. Not bad........and that's the bike I ride to this day. Need to rebuild the fork, probably, but geez........all I need is shims and seals. Cheap stuff. Got a riding friend who's a mechanic, so I don't even need to buy the tools. Just ride down the street and borrow them.
Knock off $200 in gas, $1200 a year required insurance, brake job once a year, assorted maintenance, car payment.........I don't spend two bucks on energy bars, I buy bananas on sale. Peanut butter sandwich in a Tupperware container. Something I buy in general anyway, so no real extra cost there, I'm gonna eat that even in the off season. I probably spend.......oh, $200 a year on riding. If that. So figure nine years, bike plus annual cost, I've probably spent $2500 or so. Even if I go downhilling on Killington, I get the lift passes for free, if I don't ride up (once a year, I'm not a masochist here). Not bad, I'd say..........I've spent four times that on computers that do me almost no good.
Health......somewhat. I've had two disks removed from my lower back, biking wouldn't help that. Probably made it worse. Same with the nerve damage from neuropathy I deal with now. Cardio health, yes, and just overall bloodflow and fitness, it definitely makes a difference. But it's not a general cure-all. Makes me feel better, though, and on long walks, I'm not the one huffing and puffing after a mile or so.