Valuing an LIC condo with a massive patio

I'm considering a bid for a 2Br/2Ba condo in a new construction building in LIC with 15yr abatement. It's on the 2nd floor and has ~1,000sqft of interior space, with a 1,300sqft patio lacking views. Asking price is $1.4MM. Similar units without the patio have gone for as low as ~$1,075/sqft, and this unit has been on the market for >3 months. The patio also increases carrying costs by ~$200/month in CC+tax. I've seen the rule-of-thumb that outdoor space is valued at 20-50% the cost of interior space; but that seems very high here. Sure, a patio is nice, but what's a reasonable offer for this place ? And how much harder will it be to sell for a good price in the future, given the giant patio?