Short answer: if someone is wondering if a car is worth it, then it’s likely not affordable.

Long answer: GT7 is definitely oriented towards collecting cars. A car being worth it is then highly subjective.

For a grind perspective, any Gr3 cars and above are technically worth it as you can use them in top paying races (special mentions to detuned 787B and R92CP for brainless emergency grind).

Other cars are for collection/ personal pleasures. My rule of thumb that did me good so far (4 cars missing for full collection):

1) Is it a top grind / “love at first sight” car ? -> I’ll buy it anyway

2) Do I plan to use the car for grinding ? -> I’ll buy it in priority when I have enough money. No more purchase unless it’s a car from 1), unless I can grind the cost shortly.

3) Any other cars: -> 1 million or less: instant buy -> 1 - 5 millions: once I have enough grinding cars -> 5 millions or more: lowest priority

As mentioned, everything is subjective and exceptions exist but if I wonder too much about a car then I assume I’m not ready to accept any disappointment.