I would have thought any discount would still be worthwhile.
I'd go back and ask for $600 each for this group buy - given the possibility that it could be over 50pcs. Plus shipping and paint etc. I got quoted $750 for a Carbonda Fm1001 so still a fairly decent price. $100 more is about £70. Not the end of the world.
At worse, it's a no and either carry on at $630 or bin it off and it's individual purchases as $680.