BPK was a cheaper flip than a ground-up RIV. Sure. But they didn't price BPK/VGF2 accordingly cheaper than RIV. Didn't they all have the same/similar base price/pt?
So what difference does a target profit level on their capital outlay make here? I don't think the fire sale on VGF at its end happened because it was cheaper to complete and generous ol' Mickey said "hey, we recouped our costs, now let's give back to the
DVC community."
OP's question was "Are fire sales a thing when resorts are close to being sold out? Have they done this in the past before?" The answer is yes, it happened with VGF.