Short Answer: Its cheaper and more convenient.
A lot of people wonder whether they should go to a store to buy their contacts or buy them online. The choice should really be an easy one. I run through why it is much better to buy them online than in the store.
Time
When buying from a traditional store, you will have to get in the car, and travel down to the optometrist and then discuss with the staff in store the contact lenses that you require. Just trying to find a park at the local shopping centre can be time consuming in itself.
When purchasing your contacts online, you do not need to leave your desk. Simply login to your preferred contact lens online shop, and search for the type of lens that you are after. Enter in your prescription details and then checkout.
The contact lenses will arrive quickly at your door. Some web sites even allow you to auto renew your prescription so that you wont even have to remember next time to order your contact lenses.
Money
When you consider the overheads that it takes to run a store, it really makes sense why contact lenses are so much cheaper when you purchase them from an internet web site. When buying online you are really paying for a no frills service without paying for the shop front, advertising, or the staff that it takes to man a store.
From where I see it, the choice is easy. Buy them online and save yourself money and time.