You mean clip-ons? They’re neat in theory, but my glasses are already relatively thick by virtue of my bad eyes, even in lightweight. So whenever I had a clip, the weight + bulk of the glasses started to annoy me. Pricey as it is, I’d rather just have two sets of glasses then.
I guess they could be called magnetic clip ons. I have terrible vision myself (-6.5) and require thicker lens (which zenni doesn’t actually accommodate I had to buy from elsewhere) and I never found the added weight to be an issue. As far at price, I only paid 150 cdn for the glasses which is one of the cheaper pairs I’ve owned.
Personally I hate having to carry around two pairs of glasses, it’s annoying af but if that’s what you prefer, you do you.