The question, though, is simply this: is the regret more reliable than the choice? I believe we should trust our choices more, basically for justificatory internalism reasons (we decided on the basis on the information then available) and a related set of concerns insofar as inter-temporal judgments might better be modeled on inter-subjective judgments.

I'm not sure what your concerns about luxury goods have to do with regret-as-luxury, as everyone may have regrets.

I'm not saying all luxuries are somehow hypocritical or wrong, though I do suspect that a good account of luxury will entail recognizing that there was some necessity that would have been better-served. There are no supererogatory choices to indulge in luxuries, and the Lear Jet and the Mega-Yacht really are irrationally wasteful; desires for such signalling goods are inefficient, indulging those desires is probably immoral. (The same thing goes for fine clothes or consumer electronics, of course, though to a lesser degree, and I suspect that signalling competitions in the bourgeoisie are more likely to be efficient and instrumental or utility-enhancing.)