Buying Squidoo lenses is a great way for a "newbie" to get started on Squidoo with a few lenses. Since the lenses are already created they just need to do a little tweaking. And another advantage for a newbie is that, depending on who you buy the lens from SEO is good. So you don't have to worry so much about keyword research.
Other Squids buy lenses simply because they don't have the time to build their own lenses but they enjoy Squidoo and earning money. Buying Lenses from an established lensmaster is a great way to build a base of lenses when you don't have the time to create your own lenses.
But another reason people buy lenses is simply because they want the url. So for example imagine if you wanted to do a lens about a topic but the url was already taken. You might decide to buy a lens simply because of the url.
I have seen many lenses on Squidoo that have only a few modules and the content is total crap with spelling errors. I think to myself, what a waste of a good url. If this happens to you, contact the lensmaster and ask them if you can buy the lens. Make them an offer. Think about it, you could buy the lens for $5 and then totally revamp it into an amazing lens.
Have you ever purchased a Squidoo Lens?