They may just be trying to get your price lower. I would just say "I am sorry that we wont be working together, I know I can do a great job but I cannot do this job for less than $1500
My answer now in the morning before work is different from my answer after work yesterday
Number one, for Pete's sake don't get pissy about not wanting their business, that's pointless. And at some level it's not true, you shouldn't have bid if you didn't want the business. You just don't want to compete. That's fine, nobody does. But guess what that's life in the concrete jungle, everybody has to compete. The important thing is you only want it at your price.
Now I'll hedge there and say if this customer is setting off any spidey sense that's telling you they're going to be a real pain in the ass, yeah, you're off the hook, just make a brief polite response and move along.
But realistically, you have some time and effort involved in getting this far, the smart thing to do based on the OP is spend a few minutes keeping the conversation going and see if you can win their business. The important thing here is even though your price was high, they're still interested in you doing the work, so it may be salvageable.
They may just feel like they ought to haggle. You could offer to just take $50 off as a good will gesture. You could explain to them that while you can't be the lowest priced contractor, your make it a point to be the best value. If you think they're just bluffing you could call their bluff and play hardball. Handling this step in the process well is important.
The main thing with the OP is to keep tabs on your attitude, be professional and realistic, don't take it personally if someone is shopping. Normal people shop when they're spending anything more than front pocket change. If you are not aware that people are shopping, either you live on billionaire island where nobody shops for electrical service because it's chump change like chewing gum, or you just aren't aware that people are shopping.
(BTW, I guess we've just given up on the private section for business? This really ought to be there.)