To answer the original question – yes I would happily pay a small % of bike/frame cost as a ‘Trail Tax’.
I think mountain biking still has a lot to learn from other organised advocacy groups such as the BMC, but the likes of CTC are doing good work.
I’m conscious that ‘payment’ often lends itself to a sense of entitlement and I wouldn’t want non-payment to be a ‘barrier to entry’ but that’s just down to education:
Many people [thankfully] contribute to MRTs and the RNLI etc not expecting to get ‘their money’s worth’ themselves but in order to help others in their hour of need. I’m not sure if this altruism extends to funding trails, but I’d like to think that the examples set by Lady Cannings could be extended elsewhere.