As it's their fault, but you still want them to do the work, make them an
offer!
You can plead poverty and say "I want you guys to do the work, I'm impressed
with the product and may be able to raise an additional..... but that really
is the limit".
This way both parties save face.
Make sure you leave a bit back though.
So if you think that an additional 400 will swing it and you would be happy
to pay this, offer 350 so they can barter you up a bit.

Phil