Big numbers have their advantages as well; if players have 5000+ HP, then it's easier to have status effects and the like that are supposed to inflict very small amounts of damage that add up over time. If players only have 50 HP, then that's impossible. Not to mention, there are few things as awesome as hitting for ridiculously high numbers towards the end of the game; it really lets players see how much more powerful they've become since the beginning.
While I agree with you about the gold situation, we also want to make sure that we don't make realism get in the way of practical gameplay. End game equipment and materials should cost much, much more than the player would ever be able to get at the beginning of the game, so using high values is necessary. I've always figured that one "gold" doesn't necessarily mean one coin. Coins could be worth 10, 100, or even 1000 "gold." Players shouldn't need to worry about exactly what coins they have on them, though - can you imagine a player having to go to a store and ask if the owner has change for a 1000G coin? Thus they are only presented with the value of the money they have on them, not the actual number of coins.
I'm not saying your ideas are bad ideas; I'm just presenting the opposite end of the spectrum for everyone to consider.