They may be overvalued, however they blatantly are providing an extremely valuable service. And if it were easy to replace or compete with (ie something of low actual value), the airlines etc would have already cut out Priceline and would keep the $2+ billion in annual profit for themselves (they've tried and failed repeatedly to cut out Priceline, which further speaks to its immense value to consumers).

I'm more surprised that you're holding up Tesla as a counter example to fluff valuations given their present valuation versus other car companies with actual immense profit such as GM or BMW.