I think I follow you. And I love the Myopic Cheapskate
I'm -6 to -6.5 with astigmatism, so I tend to get stuff that works, rather than stuff that's cheap. That said, I used insert RX glasses from Eassun and Adidas for a good ten years or so.
I managed to get a pair of Gazelles with insert (no RX) on the 'bay a few years ago for £15, and a further £20 for the glazing. They seem to have gone up in price since, mind.
A few arguments for getting the tinted external lens:
* you can swap them out during a ride (of course, yiou swap between the tinted and untinted RX inserts)
* If you scratch the tinted outer lens, the lenses are cheap. The RX inner is likely to be more expensive to replace
* Different tints for different light conditions. So, for example, I used a dark tint, clear, yellow for low light and polarized for sailing, where the light conditions are pretty harsh and the polarisation sometimes helps with spotting the breeze.
* With the heavier tints, you look like you're wearing sunnies, not like you're about to go and interfere with the livestock at the local petting zoo.
I'm not sure if those are compelling reasons, but what the hey. I still would suggest stumping up for some proper nice ones from Optilabs. I found a pair improved my riding far better than any £180 part I ever bought for a bike.