You got Prem Eco for $2,750/person round trip from the East Coast U.S. to Japan. I think that is fair price, neither good or bad. Full or Fully Flexible Prem Eco fare from the East Coast U.S. to Japan tends to be somewhere around $3,250 - 3,750/person round trip. As evergrn indicated some airlines (usually Chinese airlines or Taiwanese airlines) provide some cheaper fare and require flying to China or Taiwan.

Discount Prem Eco fare from East Coast to Japan tends to be somewhere around $2,000 - $2,500/person round trip. I have seen Prem Eco lower than that but not always. I think it is unlikely that fare will go down on the airline and the route you got for this Prem Eco.

I think you got fair deal and likely Prem Eco fare you got is restricted fare, make sure you understand restrictions on your ticket.