When I got my quotes, I thought the same thing...but the pond loops didn't come in cheaper. I even considered ground loops (but didn't want to tear up the yard again). When they give you the quotes ask them for the details --the unit make, model, capacity etc. etc.----you know all the good stuff that they don't want to share with you as they know you're 'shopping'. Mostly, they sub out the pond looop work so I wouldn't be surprised if digging ground they didn't sub that out too). They shouldn't have any 'hidden' costs from you. I was lucky enough to have a sizeable rebate in Indiana that I was able to take advantage of too. Good luck, no regrets going geo here...mine were reputable and stand by their warranty, good people to deal with.
