Negotiating with Wholesaler as Buyer

[Jessica Tucker Grubbs]

I am looking to buy a mobile home park in an MSA in NC. The park happens to be an off the market deal from a wholesaler.  I ran some initial numbers and it is way overpriced. (Asking $850k and it is worth $450k-$500k - using industry-standard income-based valuation methods). 

I am super into the property, other than the price it is a great opportunity.

Wholesalers, what is my best move here.  How should I approach the wholesaler in a way that I can buy this thing for a realistic price and they can get what they are trying to accomplish done too?  Is it normal to way overprice things in the hopes of luck? (Like I said, this isn't even on the market).  I am curious about what is going on here.  And slightly nervous to screw up the opportunity as this would be my first park although I am well-educated on the topic. 

Thanks in advance!