Gwadar's importance transcends economics: it has strategic value besides the trade route itself. It is within shouting distance of the US fleet in the Gulf; it is well placed in relation to India, including its activities in ChahBahar, etc.
Very few things transcend economics, primarily religion. One may fervently
believe as an article of faith that Gwadar is supremely important, but where is the
proof of its strategic value? What does its proximity have to do with the US fleet, unless China bases a considerable fleet presence there, and even then it would be doubtful in terms of its efficacy in countering US military capabilities in the region? What does "well-placed" mean in relation to Chahbahar? The value of Chahbahar to India is in the rail link to Afghanistan being built, thus bypassing Pakistan. How does Gwadar affect that at all?
Coming to economics, the equation is never static. Shale gas used to be economically prohibitive until recently, but no more. The Chinese are pragmatic, if nothing else, and there is a concept of investing in ventures which you expect will gain value over time, especially if the costs can be amortized over time and space. It would be unwise to state categorically that Gwadar will never be economically viable and, given China's deep pockets, their outlays are mere chump change.
Your shale gas analogy does not apply here, given that it is a commodity subject to laws of supply and demand, and with prices driven down by technological advances of fracking. Yes, I agree that China has deep pockets and usually a long term view of things, but how does that help it defeat earthquakes, terrain, altitude and weather across the Hindu Kush mountains? China will look at the economics of investing even "chump change" of a few billion dollars in Gwadar's links very pragmatically and come to the same conclusions about their lack of viability. Its actions will speak louder than any words you and I might say here.
My concern about Gwadar is not about its viability from an economic or strategic point, but the security situation in Pakistan. Roads can be built and rail links connected, but it's all only as good as the weakest link which, in Pakistan's case, is the security situation along the corridor.
I would turn that contention around: It will be far easier, comparatively speaking, to ensure security in Baluchistan and elsewhere in Pakistan, difficult as it might appear, than to defeat logistical problems in ensuring commercially viable transportation links through Gwadar to western China across the Hindu Kush range, given that there are comparatively cheaper workarounds available.
For Gwadar, cold economics will prevail over fervent faith, most assuredly.