Four Swords Keys

What's the deal with the keys in FS, I know there are three different kinds, silver, gold and hero's keys, but what's the difference between them? And how many rupees do you need to get each kind?

All I know is you need 5000 rupees for the hero's keys

The difference between them is that Vaati's Palace is harder depending on which key you get.
Siver Key: any amount of money
Gold Key: 3000+ Rupees
Hero Keys: 5000+ Rupees (and you get the massive, 12 level Vaati's Palace)
But you have to get them in that order. So even if you get 5000 Rupees the first time, you still get the silver key.

Yeah thats it exactly what it is I remember how hard it was to get the hero's key in the forest.