Our lot has a (small) slope - basically when you walk out the back door, you take a 3-4 inch step down and then the back of the yard slopes back up (so the back door frame and the dirt at the back fence are about the same height). The distance from the back door to the fence is about 50 feet.

We have basically had 3 stories from the pool builders who have come out to quote us, and I just don't understand how they can be so different.
1) no comment about the slope of the yard, build pool as normal. (drains, drains, drains)
2) slope is a big deal, basically we would have to remove our existing 20 feet of paver stones and raise all of the decking to back door level (a raise of about 3-4 inches like I said)
3) put a 6 inch "retaining wall" at the back of the pool (our ideal pool plan is geometric so the back is one straight line with a raised spa in one corner). We were told this would divert the water away from the patio.

I'm not sure which story I buy...it seems like adding 240 sf more decking (plus removing our existing paver stones) is just profit-minded, but I can't fathom how a retaining wall at the BACK of the pool would do much of anything and that is an extra cost, too.

Hopefully someone else will chip in too.