HTTPS For Ecommerce?

Hello I was wondering how many here use HTTPS for ecomerce sites? I won't be receiving any credit card info as i want to process everything to paypal? Is this recommended? I plan on using shopify but I'm a huge noob when it comes to ecomerce so I don't know how the whole receiving payments process work. My specialty is affiliate sites. I see that in order to get the green letters on your site you need to pay around 100$ for an HTTP certificate. Anyone have any recommendations or way's to get this cheaper? Should i just go for the normal 10$ http certificates? Do the green letters really make that big of a difference? I plan on using the FH method so I'm curious. Thanks for any help!

I don't run an eCommerce site, but if I remember correctly, HTTPS slows down your site a bit, so it's usually only reserved for checkout and login pages on eCommerce sites.

As for the cheap or free HTTPS, check this thread out: http://www.blackhatworld.com/blackhat-seo/white-hat-seo/756144-how-free-ssl-wordpress-website.html