I’ve bought online once about 10 years ago and whilst the lenses are great, the frames don’t fit my enormous head well so I never wear them. That’s my fault for not taking the correct measurements though, so make sure you do. Measure twice, squint once or something.

Regarding complex prescriptions- my brother’s an optometrist (he wasn’t when I got my specs) and there really is a lot of work that goes into those lenses as well as the cost of the equipment to make them and the upkeep of that equipment and the optometrist’s wage and the rent on the shop etc…