Since everyone is weighing in, no this is not Price Gouging in the strict definition. I'm going to assume you actually want to know why you're seeing these different prices and that this isn't just a rant type of thread.
Northern Brewer, Williams and Morebeer have a free shipping pricing model and Rite Brew and some others like Brewhardware.com has an ACTUAL shipping model.
A free shipping model takes the item cost + markup + average shipping cost = retail price. The fact that a buyer doesn't reach the free shipping threshold has no effect on the price of the items because most customer DO reach that threshold and everyone pays for that.
Market research suggests that the vast majority of shoppers are fooled by "free shipping" even if a given vendor's total delivered price is higher than one that shows the actual shipping cost on the checkout page.
Here's why a company would NOT want to offer the free shipping model:
For one thing, as you've noticed, it just FEELS slimy as hell when you really notice it. Second, it slaps local walk in customers with a markup to cover costs they will never contribute to.
Here's a best case shipping scenario, like in state or adjacent state to NJ:
If I change the address to California, it looks like this:
If you want some extreme transparency, I'll play along.
The cheapest I can get Briess DME 3 pound bags is $7.39 with maximum volume discounts, not including the distribution of a couple hundred per pallet in freight costs. I have to personally, or pay someone to break the pallets down, check them in, put them away and update the website's inventory. It gets stored in a space that costs rent, heating and cooling, lighting, insurance. I pay $850 a month for the website. Visa takes 42 cents + 2.2% of the order cost. I have to buy boxes, packing tape, and pay someone to print the orders out and pack and label the box. Every step of this process is more cumbersome than it actually seems. You have to account for the calls when customers want to cancel an order or change an item. You have to account for lost boxes because all the carriers suck. You have to account for shipping clerk mistakes, when they ship a similar but wrong item. Sometimes the DME bag breaks open and makes a mess and things need reshipping. Sometimes the box ends up being an inch too big in one direction and it costs me $5 more than the quoted shipping cost.