My driveway has slowly been sinking.... here's why:

The garage is under the house, and the original driveway sloped down
about ten feet. The previous owners filled it in (no access to garage,
now have a level driveway).

I need to redo the driveway so it's level (or slopes slightly towards
the street, away from the house).

I got three bids. Two said they'd tear up the old driveway, haul away
the rock, and put down a new driveway (4 inches, if I remember right).
Around $2000.

One contractor said he'd just put the new one on top, $700.

I suppose the two contractors would say that doing what the third guy
suggests would let the driveway continue to sink. But I think it's the
fill that's sinking, and their 4 inches won't stop that.

Is there any reason NOT to go with the cheaper version? I figure that
if in a few years it turns out the first two were right, well, $700
wasn't much to spend to take the chance.

Thanks,