Let me put it this way - on my Plus account, where, with the exception of 3 days, I played daily since mid-April for an average of a half-hour, mostly grinding the two (three until PD nerfed Tokyo) most-lucrative races, I am still over 200,000,000 Cr. away from owning every car, even if I sold my remaining 36 duplicates.
To put it a second way, if one excludes the 2,200,000 Cr. between the pre-order, 25th-anniversary, and "make-good" credits from the 1.07/1.08 disaster, I have acquired 267,221,890 credits between race winnings, championship winnings, missions, license tests, circuit experiences, the roulette wheel, and car sales. Between the initial 39 menu books, license tests, and missions to date, the cars won were worth just under 24,000,000 Cr. if purchased. The cars won in the additional menu books, in the extra menus (no, I didn't abuse Luca on that account; I only took delivery of one Honda NSX rally car), in roulette spins, as a birthday gift, and as a trivia prize add maybe 12,000,000 Cr. if they had been purchased (and a few were sold back).