Price error?

Last night I booked 3 economy return tickets f LGW - BOS n Delta metal for 150k on miles and a total of £255 in cash...

Is this going to be a pricing error or is it is a new route promo?

Is this one way or return? Miles seem right for a return, but taxes seem too low. Unless the fact it's on DL metal changes things significantly (I don't know).

Yes, have searched again and its showing this price for certain dates in July/August.

Have looked at the breakdown and it shows:

Carrier imposed international surcharge (YQ) £0

United States APHIS Passenger Fee Passengers
£9.00
United States Customs User Fee
£13.50
United Kingdom Passenger Service Charge Departures
£44.16
United Kingdom Air Passenger Duty APD
£160.00
United States Immigration User Fee
£16.20
United States Passenger Civil Aviation Security Service Fee