Sealing,
The comparason a to the likes of TCX (for other routes)are mainly around economy given TCX don't offer a J cabin, especially around things like AVOD
This is where you see MAN-ORD around £1140 Rtn (some days higher, some days lower but that's the average) in December. LHR-ORD comes in around £1200-1500, which isn't a huge difference in the grand scheme of things.
The £999 Boston, while agree is dirt cheap, was an introductory offer IIRC.