I'd probably take the offer, especially if your econ ticket was pretty cheap.

Typically my target for 'good value' upgrades is $1/min for domestic F and 2-3x that for international D1 especially if its a redeye. That route is typically 9.5hrs+ which is closer to the 2x side of my range.
And you'd get to use the JFK D1 lounge for a nice dinner/beverages prior to the flight if you want to get to the airport a bit early.