I looked at this a little closer, and my theory seems to be incorrect. Unfortunately, priceline does not make researching this easy. While they have links to the fare rules for the flights they are quoting, they don't display the fare basis codes anywhere in them. So it is difficult to know exactly what they are quoting (plus there is no fare breakdown between the two fares). The fares they are quoting doesn't actually add to up to the combination I thought they were quoting. A QVAKZNB3 fare plus a SVAHZNB5 fare should add up to $162.20, not the 156.20 they are quoting. If they were getting the married segment inventory wrong on the LAX-EWR fare, I'd also expect them to get it wrong when booking LAS-EWR standalone. But they don't, and quote the correct $155.00 GUAHZNB5 fare when attempting to book the LAS-EWR itin by itself.

I'm thinking this might be some kind of priceline bulk/consolidator fare combination. Note that it's very close to the UA BE fare being quoted for LAX-EWR -- a single KAA4AQBN fare for $156.30. The fare rules shown on priceline have some odd language in penalties/blackouts/etc sections that I don't find when looking up AA fares on EF, aa.com, etc (see below). Don't have any idea what NCNG and DGR are referring to.

UNLESS OTHERWISE SPECIFIED NOTE - RULE NCNG IN DGR APPLIES
FOR -B3 TYPE FARES NOTE - RULE 11B3 IN DGR APPLIES
RULE 395K IN DGR APPLIES