It's a catch 22.

At times like this you've got their ear because you were clearly right. The problem is that they think it's going to retrace back to $58k or whatever. 

Tell them that this is the last chance that they can buy under $100k.

Tell them that it's ok if they don't buy, but that in 4 years time I'll be telling you this is the last chance to buy under $1M.