Surprised that P4 costs only 9 milion credits. I was expecting 20 mil like in GT Sport. After the update which increased rewards i thing this GT is one of the most efficient ones to buy new cars.
It isn't close, though the update has made it more efficient than GT5, GT6 and GT Sport, at least on the face of it. Not sure when you compare the Seasonals in GT5 and 6.
GT4 was super efficient once you reached certain points, 2 laps and less than 3 mins netted you about 250k and the DTC championship netted you over 1m Cr and you could speed through that pretty quick in B-Spec (about 10-15 mins IIRC). In addition, the most expensive cars in GT4 were 4.5m, not 20m.
GT2 netted you 550Cr in about 5 mins, and the most expensive cars were 2m.
So GT7 lags well behind both of those in the time it takes to buy the more expensive cars and it is only really efficient when earning Cr since the update in comparing to the more recent games.
That said earning over 1.5 per hour isn't terrible, it's a huge improvement on where it was when the game launched, but there needs to be more races availalbe to do that in and more races in between the lower rewards and those with a bit more variety, not just 600pp, 700pp, 800pp etc.
And not missions and endurances in the missions with one-off rewards either. There was no reason those 1hr endurance races couldn't have been in the World Circuits which would have given them more replayability.