RV to House electrical hook up
For the full 30A load, the least expensive option that doesn't involve a direct bury cable would be to pull an aluminum 2/2/4 direct bury URD/USE triplex cable through 1" Schedule 80 PVC conduit, although it'll be a very tight fit (234mm^2 used out of 236mm^2 available).  If you wish to go with Ed's 24A number, I'd use a 6/2 W/G UF cable instead -- NM has no business being run in outdoor conduits!  While you could run individual 4 or 6AWG copper THHN/THWNs in the conduit, that'd be a bit costlier than the UF or URD cable, especially for 4AWG.

(If you use the URD/USE cable -- the 2 AWG wires are the hot and neutral, while the 4 AWG wire is the grounding conductor.)