It should scale with the game, low payouts to start with, huge payouts by the time you've finished everything. There should be more of everything, as well.
Events should, as you say, be scaled in payouts by time driven.
There should be 10+ events, 50+ individual end game races that ALL pay roughly the exact same amount per minute. These should be the hardest events, like the old days. Championships, individual events, they should all pay the same, give or take a few thousand to account for people using different cars.
Custom events should also pay the same rate, as should online events. Online events could scale up in terms of your DR, and the level of your competitors. If you're DR A and beat 15 other DR As, it should pay very highly. Still primarily based on time though.
As for the big question of how much, personally I'd be happy with the end game rate being around 2 million per hour. That would still mean that to buy every car, and earn enough credits to modify a large number of them, will still take you about 210 hours.
That seems perfectly reasonable to me, it's not "in five minutes" and in line with the old games. It's half the time it'd take grinding the META event currently, but more importantly, you could earn that rate ANYWHERE.
Again, these are end game events and rates I'm talking about, top level online events, and custom races against the hardest AI once you're at a high level/unlocked everything. I'm not suggesting events at the start of the game pay this much, or that every event does.