If it helps, the cheapest I could find (in a 5 minute search) for a 7 night stay, admittedly on 30 June, was SVG-LHR-JFK/LGA-BOS-JFK-SVG, for £867 return in Club and domestic First, which is also a tidy 420 TPs. £898 for 15 June / 7 nights, CPH-HEL-JFK-LHR-CPH, Finnair out, BA back. And an extra 2 quid to go via LHR rather than going to HEL! £872 for BLL to JFK, Newark back, both via London.