A battery pack for a Model 3 is $10K. So even if the whole car is only worth $20K, it's still worth keeping on the road.
The Porsche Taycan battery pack is $70K. The moment you have any issue at all with it, the car will be considered totaled.
Huh? The taycan has an 8-year/100k mile battery warranty. How many 100k+ mile carreras do you see for sale on eBay?
I've driven a 2003 Volvo S60 (plain 5 cylinder, no turbo), which matches your 20 years - and most diy repairs were quite straightforward. I suppose you're talking about some Mercedes or other brand I'm less familiar with?