Sorry, the MB is a compromise. Performance for portability.
But then so was the 1st Gen MBA? I bet that if one would go back, and check commentary aimed at the MBA, in comparing it to the MBPs of the time - one would also find the "sacrificing power for portability" etc. etc. arguments made there, in pretty much the same fashion as is being made here...
Would I buy a rMP? Probably not. I need 16GBs of RAM to run virtual machines, video rendering etc., and I appreciate the extra grunt - a worthwhile compromise for the (slightly) bigger weight/size etc.
But were I to have a current MBA, or were I to be considering a MBA since I only do X/Y/Z that doesn't require the extra grunt under the hood - then the rMB would certainly have entered my frame of reference...
Different strokes for different folks. And yes - there might be PC options that offer 'better' specs, for less price - but to simply call them "better-valued" on the basis of specs, leaves plenty out of the equation.
I'm heavily invested in OSX - yes, it's not without its issues - and yes, Win10 might be a huge improvement - but until the Windows world offers me the ease of use to construct workflows like I can in OSX, any PC will simply not be an option for me.
And until a PC, specs aside, can offer me the same user experience of a Mac trackpad, and the OS integration therewith, it's also not an option for me.
So, in *my* world - PCs offer better specs at cheaper prices - but that's where it ends. I will still get "more" out of a MBA/MP/MBP running OSX, and I'll gladly pay the price premium. It remains "better value" for me to do so.