Mulv, NICE will decide whether they are beneficial enough to be prescribed on the NHS and under what circumstances. And if the decision is in the “give it a few years” timescale, they’ll be off patent too, so relatively cheap. (Although because PCSK9 inhibitors are biologicals, bioequivalence will be harder to prove)
Drugs do come off-patent fairly quickly. Viagra, for instance, has much cheaper competitors with the same active ingredient now that Pfizer’s patent has expired.