$7,500? It looks like these have ascended into cult favorites like a 57 Chev.
These deserve that status, but for me I wouldn't buy anything that I have to baby to preserve its appearance and resale value. Its just a working tool after all.
For a price comparison there was a clean one (or was it a 186D?) on ebay around $6k for many months.
The previous model YM186D will do the same work, its nearly identical. YM187D was an upgrade with slightly longer wheelbase so more comfortable for the operator, and transmission said to be upgraded. I don't see anything about my 186D's transmission that could be improved. It does feel tight to dismount, no other problems.
Maybe the guy is bluffing on the price. Offer him $5,500. Seems to me that would be top dollar unless it looks showroom new.