I agree with that to an extent, I'm guilty of buying a bike far better then I'll ever need, but other than upgrades I want to do and maintenance I can't see it costing me another penny. I built my Onone out of second hand gear other than the frame and brakes and that cost just over 600 with a pretty deecent spec sheet of hope, crank brothers, marzocchi and slx group set, that things been everywhere too and got ridden pretty hard. You can go as mad as you like in the mtb world but at the same time it doesn't have to cost you 3k+ to get you going.
The clothing thing I'll agree with, I bought an ixs lid and knee pads/brace based on reviews of how good they are, other than that I own nothing else that you'd class as enduro or mtb or whatever, just t-shirt and a base layer I own because it's cold at work. Isn't the trials/bmx world guilty of the same thou? Black skinnys - 3/4 sleeve baseball tee, with mid tops thrown in just for good measure...