SRAM applied for the patent before anyone else started making the parts. Yes, they can ask for retrospective licence fees & damages, just as Apple did to Samsung in the USA.
However they are not abusig their position. There are alternative chainsets available, just not with this particular feature. We don’t have to buy thich-thin rings, after all.
It is possible to patent a new application for old technology, in this case for lightweight bike chain drives, using the thick-thin principle. An example of this is the extension of drug patents from one disease to another indication (eg Botox, Viagra)
Even if they’re able to rein in the copy market now, the genie’s out- we know a little company in England can make rings that do the same job for £35, so even less people will be happy spending £70 for a SRAM one.
But it’s not about the manufacturing cost, it’s about the value to the user and the cost of the R&D. For instance, bringing a new drug to market costs up to a billion US$. The drug might only cost pennies to manufacture, pennies to market, but they have to get back those R&D costs somehow. That’s why prescription drugs cost so much and why patent protection is needed. Viagra, for instance, is just about to drop in price by 80% now it’s off patent in the UK. Its price will remain high in the US, and is dirt cheap in India where they don’t recognise IP so effectively. (They also have a habit of not making to a high purity, but that’s a different story)
So just because a UK company can charge £35 instead of £70 for a knock-off, is no reason for saying the higher price is not justified. The manufacturing price is a small part of the overall cost for originating products.
By the way, Sustrans’ part-time lawyer spent many years in patent law. He might be interested in some consultancy!