£60 is hardly a bargain!
Don’t think I’ve ever paid more than £30 for a cassette (granted I’ve not replaced an 11 speed yet)
Its decent price for 11 speed, compared to equiv Shimano (and much cheaper than SRAM ones) plus once you've seen the light switched to a Miche cassette, you only need to replace the worn sprockets, not the entire cassette, as its generally only the teeth on the middle sprockets that get worn, so with regular cassettes you bin the whole thing for the sake of ~3 worn sprockets. Miche cassettes are all individual sprockets and spacers, not a big bonded lump.
As you've hinted above the cheaper option
may be to swap in 10 speed off another bike and sell that with the Ultegra triple set up on it - whilst you or your LBS is changing one bike they may as well do two - might not cost too much extra. I'm not sure what is more attractive when selling that bike, Shimano triple or SRAM double, depends on buyer I guess, but if its a frame that could be used as a tourer, then a triple might edge it.
If you spread your miles out over your stable of bikes things wear less quickly...i.e.
I only run 11 spd on one bike, the best road bike, which doesn't get ridden in winter, as no guards, so the replacement cassette issue doesn't come around too often & KMC 11psd chains are cheap enough in "normal" times. The do-it-all gravel / winter road / light tourer seems to gets ridden the most and its 10 spd and has 2 sets of wheels.
Being nerdy I'd I've just checked veloviewer year to date stats, I have done a smidge over half my miles on the gravel bike, c20% on the best road bike and 30% on one or other vintage steel bikes - the balance of those is normally reversed, but I had a shifter break on the best road bike so rode my steel ones more whilst I got that sourced and replaced, and one of the steel bikes I bought & did up this year, so it got more attention!