I splashed out on fancy specs with Rx transitions lenses 3/4 years ago (I got Oakleys but I tried on other brands, what matters most is fit). Yeah, it was £300 or so, but they made more difference to my enjoyment of riding than pretty much any other chunk of money I’ve spent on bikes before or since. They just stay solidly on my face much better than normal specs or even cheaper ‘sports’ Rx glasses. I can use them in bright sunlight and for night riding. I’ve crashed badly enough to need carting off on a spinal board, totalling a full-facer, but they survived with just a tiny scratch on one lens. Given that I’ve done well over 300 rides since I got them it works out at much less than a quid a pop, and they’re still going strong (not to mention that you can use them for loads of other stuff too).
Yes, it’s a lot of money but frankly I’d rather ride a cheaper bike with good glasses than a bike costing £300 more with crappy glasses. Being able to see where you’re going is kind of important…