The fact that money is far harder to come by in GT5 than GT4? I remember in GT4 I simply had to keep doing Cote d'Azur Rally 3 laps over and over and each time I'd get about 1.3 million credits. With GT5, it forces you to really think in the earlier events what cars to spend your money on. No more willy-nilly just spending left, right and centre. Same way, you only win prize cars ONCE, not 50 times and sell them for 500,000 credits each time.
I'm appreciating my cars far more in GT5 than I ever did in GT4
I'm appreciating my cars far more in GT5 than I ever did in GT4