The grind isn't 3000 hours... 3000 hours is the time it would take to get all of that (all cars + tuning parts) by just playing normally enjoying the game, gaining an average of 200k per hour with custom races/sport mode.
That's waaaaaaaaaaaay too much. No way in hell am I ever going to spend this much on GT7. Or 99% of the playerbase for that matter. Even 300 hours is the equivalent of gigantic playthroughs of AAA games like RDR2 and this is the time it takes while GRINDING, ergo, boring replays of the same races over and over.
This game has a checklist for you to collect cars and it was made blantantly clear that you have to collect them, given the fact that PD releases extra menus about just collecting cars, means you really can't get away by not having to buy them all for the ultimate experience. Not to mention some of those cars are also fan favourites (McLaren F1, 917k, CLK-LM, Shelby Daytona, McLaren F1 (both race car versions), the Group C cars)...
Credits have never been so scrutinized in a Gran Turismo game, ever. And without them, you really can't experience the game to its fullest. As I posted before, tuning by itself is extremely expensive, with majority of the cars costing 500k to fully tune.
You want to know one more thing? Most of the World Circuit Races make you LOSE money rather than gaining. This last menu book, the one with the Neo-Classic race cars, I had to give it a go at them several times to beat those races. I had to buy Racing Hard/Intermediates/Wet tyres for all of my Group C cars, plus a full customizable racing transmission as well because tuning was 100% required to beat these races.
You basically waste 100k more or less on tuning to get 150k prize money for winning... And this is the best scenario where you get the right car and right setup on your first few tries, as I said, I had to try several different cars for each race where for each of them I had to buy all those sets of tyres and the racing transmission, so with 2 cars for one race, you actually lose money.
^This is something a lot of players are yet to realize. Sure, I could always have set the AI difficulty on Normal or Easy, but that wouldn't exactly be at all challenging right?
And on top of that, the payouts are not grindable either, at less than 1 million per hour lol, so basically, all that effort for a one time race that you likely won't touch ever again... I sure won't, given it's not really a race but more of a "mission" than anything where I have to detune my lovely Group C cars to be absolute pigs while the AI starts with their normal speced Group C cars at the front of the field some 15 seconds ahead at the start.