$300 for lenses is too expensive just normal lenses and not transition or bi-focal lenses. You could try another optometrists, I am sure you should be able to find a cheaper place.

Personally i don't buy my lenses online mainly because my private health insurance covers most of the cost and I only end up spending 50 or so dollars in total. Make sure you take into consideration that most of these online shops won't be covered by your health insurance and so could end up costing you more.