Tell them what I usually tell my customers when they want something cheaper...
"There's always gonna be a way to buy something CHEAPER..that's why God invented China"
or when they ask you what your BEST price is..
"Well the list is $35,000 but I'm selling it for $45,000.." When they look at you in confusion tell them "You asked for my BEST price..if I can sell it for that, then that would be MY best price!"
It's fun to see the reaction when the tables turn like that