That fare constructions is called "sum of the locals" where it may be cheaper to have multiple independantly priced fares (usually where LCC's fly and fares are matched) than one fare priced from origin to destination (where there are not LCC's and thus the competitive fare is higher.)

HAX is just a 1 way H fare that is matching a particular LCC in that market. In this case, it is WN. Based on your outbound travel date's advanced purchase and maybe stopover time, pricing like this is most like cheaper than the going rate for CMH-LAX.