IANAS, but you may be introducing bias by offering pre-determined choices for cost. Perhaps a Google or Wufoo form with free-form entry would reduce bias. Samp

IANAS, but you may be introducing bias by offering pre-determined choices for cost. Perhaps a Google or Wufoo form with free-form entry would reduce bias. Sample questions: a) [radio] prefer one-way or round-trip? b) [radio] do you want wifi? c,d) [textfield] how much are you willing to pay for a wifi (one-way trip|roundtrip)? e,f) [textfield] non-wifi (one-way trip|roundtrip)?