I have had several people suggest that I start charging for my Price Comp list that I send out weekly. I do not feel right forcing people to pay for it and I am afraid that it would create more work for me (keeping track of who has paid, who hasn't, who gets the email that week, etc.).
I put this feature on my blog for anyone who WANTS to pay for the list. It's more of a "donation". If you want to donate, I will definitely not stop you. If you don't want to, don't worry about it!
(Payments are made through Google Checkout and are completely secure. It is similar to a Paypal type set-up.)