...you've had this conversation so many times you can head it off before it happens:
"Wow, that is way too cool, can you build one for me if I pay you?"
"Sure"
"Awesome, what's that usually cost, $4-500?"
"$1500"
"But you said you'd build it at cost!"
"It would probably cost $2000 to actually build"
"No way, now you're just trying to make money off me"
"Suit yourself"
...or you've actually gotten partway into a build and the person decides they don't
really want to pay what they said they would... you know, the $750 they said it would be worth... now that it's approaching, they feel like paying $450 instead.
