Mamma mia. Re: the BMC price, that is just plain silly. Fly to the US or Italy and find a super-duper small framebuilder to set up a frame in unobtanium for you for about a third of that amount.
This is pretty obvious, but this is my take on increase in demand:
I reckon it's been gradual over the last 15 or so years -- firstly, as a crossover from triathlon, then (and more so) as a corssover from the popularity of mountain bikes, and then from the increased coverage of The Tour in English speaking countries
There'll be more than just those factors. If you look at the current crowd, there's quite a few of those men in MLC on fancy bikes. At the end of the day, there are only three recommended sports, jogging (boring), swimming (not getting anywhere) and cycling. Then there's the fuel and environmental issues along with traffic congestion in cities. In our local area, the improved cycling facilities (bike path) also contributed significantly to this uptake.