No, that's not what I was doing, and in fact bitched about item prices being higher when bought thru prime. If an item cost $5 plus $5 shipping and $9 with free shipping under prime, then, how much free shipping are you getting? Someone is lying, both can't be right. I'm absolutely certain Amazon used to do that, not sure if they still do, but they did, and I bet they still do.
My kids have Prime, I sometimes buy through them if the item warrants it. Mostly I just add stuff to my wish list and when it gets high enough for free shipping, I buy it. Everything they sell doesn't qualify for free shipping, and everything doesn't qualify for prime, so due diligence is required. I've been screwed more than once when I paid stupid prices for shipping that I thought was included with the free stuff.
Another nasty habit I noticed is sometimes an online search will find the item on Amazon at a low price. If you go off the page and do a search directly on Amazon for the exact same item, it comes up with a different price and you can't get back to the original price. They obviously have a number of pricing schemes to get into your pocket. Another reason Amazon loses trust from me. They are a shaky out fit and if you are price conscious (cheap, like me) due diligence is a must.