(Yesterday, 11:25 am)OrangeArrow49 wrote North East Regionwide duo is £18, so, works out at £9 each, if you stay together for all journeys, which you would be for a return. Sounds expensive but covers all of the North East, so is good value really

East Durham All Zones duo is £11, so £5.50 each, compared to £6.20 if bought separately. Apparently East Durham single is £3 (not sure about singles between Peterlee and Hartlepool specifically though) so duo for East Durham zones looks the cheapest to me (I could be wrong).

Only journeys that are completely within the NECA area would be £2.50 capped.
So Peterlee to Hartlepool would be £3 capped, as its x-boundary into Tees Valley.