Backing is an act of goodwill... IT IS NOT A PRESALE. People who backed 5000 or more will not get perks "worth" 5000 by a long shot.
You back a game primarily because you want to see the game be made, not because you are getting perks. Without the backers' goodwill, the project would probably not even exist. People back more early in the campaign so the whole thing gets off the ground and in the end the game gets made and is available at a normal price to the public.
Economically this almost always means early backers pay a higher price than late backers, yet receive the same product (plus maybe a few perks that cost little or nothing for the game developer to actually make).
Hardly anyone seems to understand that kickstarter is not a pre-sale platform. It is like sponsoring a fine artist because you like their work, or paying for the recording of a demo tape of your son's garage band. You do not do it because of the actual value of goods you receive in the end, but because of an intrinsic motivation because you like what you see.