If you are not familiar with "Availability Groups" and "Price Groups", please check them out first as the following builds on what was discussed before.

You can use both the availability groups and the price groups to give your customers different prices, access privileges, and easier navigation.  

One of the ways you can use both availability groups and price groups together is when you want to have a wholesale area in your retail shop.   You can take all the products you want to offer to qualified wholesale buyers and put them in a "Wholesale" price group.  Merchants will sign-up for accounts and you will add their accounts to the price group so that when they login they see the wholesale price.  That is standard "price groups" so where does the availability group come in play?  Well, let's suppose that you want to have only certain items offered at the wholesale price while other items you do not sell at wholesale.  In such a case, the wholesale customer will have no way of knowing which items offer the wholesale discount unless you send them a list, or by trial and error.  

To make their lives easier, you can create a category and call it wholesale.  Put it in an availability group and assign the wholesale customer to that group.  The category will not show except if the people assigned to that group login.  Now, under the wholesale category you can assign all the products that are offered at wholesale.  You do not need to worry that those products will "disappear" from the store because they will NOT, unless the individual products are assigned to the availability group too.

Example;
All products: (All customers see them at retail price).

watch $10
earrings $10
pendant $10
scooter $10
doll $10
clock $10

Assign the watch and earrings to price group called wholesale at 50% price and assign John to that group.  John logs in and sees those two at $5 each and all the rest at $10.   If you create a wholesale category and assign it to an availability group called wholesale (it is OK to have a wholesale price group and a wholesale availability group), and assign John to that group too.  When he login, he will  see the watch and earrings at $5 each and all the rest at $10, and he will  see on the category tree a link that says wholesale, while other people WILL NOT.

Now, if you assign the watch and earrings to go under the CATEGORY wholesale, when John clicks on it he will see them there at the same price he is to get which is the 50% price.   He will also see them under the other places they are normally in ALSO AT THE 50% price.  He will also see the rest of the items in their categories at the normal retail price.  ALL customers other than John will see all categories except the one we called wholesale, and they will see ALL items in their normal categories at the retail price.

IF you assign the watch and earrings as assigned products to the availability group called wholesale, then John, after he logs in, will see all the categories, with the watch and the earrings under their normal places, he will also see the wholesale category and under it again he will see the watch and the earrings.  Anywhere he sees them they will be the wholesale price, but having them under the wholesale category tells him specifically which ones he is getting the wholesale rate on so if it is not there he will know that it is NOT offered for wholesale but then he is free to go and buy it at retail.  ALL other customers will naturally not see the wholesale category (just as before) but on top of that, since you now assigned the watch and the earrings to the availability group, all customers (except John after he login) will NOT see the watch and the earrings.

Another way of using the combined effect of price groups and availability groups is in situations where you want to have multiple price groups for various member levels.  Each level gets a different price/discount and by creating a category that has each level's name, memebrs will see their relevant "category" when they login and that category could either be used to list the products they can get at their respective discount as outlined in the first scenario, or see the products that is only available for them as outlined in the second scenario.  Additionally, you can use the header of the category to communicate with them or offer them targeted products based on the profile you have of them.