It depends on the city pairs and dates. looking at google flights for me. AVL-ORD the round trip is $179-299 on a random dates in march/april, the one way AVL-ORD is $90 on certain days but $225 on others, and the ORD-AVL leg is at minimum $170. This is for the nonstop UA and AA services.

For your example of IAH-LAX its between $90-190 for the oneway and the same in reverse depending on day, the round trip is $200-300. both directions are $90 in march for example.