Multiple unit of measure in QB is poorly implemented, but if you want to use it, you must have the accountant, contractor, or manufacturing edition -for some strange reason intuit does not think the retail edition needs multiple u/m

You set the base unit to the lowest unit you buy or sell, each is usual

then you create related units, case = x-number of base units, pack = x-number of base units, etc

Then in the u/m block of purchases, or sales you select the u/m you are buying or selling

see this for why I say u/m is poorly implemented
http://onsale-apparel.com/Rustler/tag/um-good-and-bad

custom pricing is done with price level lists.  You can assign the price level list to a customer on the customer record additional info tab (in 2013 and up on the payments tab)---- and/or select the price level list in the rate block of the invoice or sales receipt. One price level list can be used for as many customers as you wish, like a retail and wholesale price level list for example.
Menu Edit>Preferences>Sales & Customers>Company tab > check mark use price levels to turn on price level lists. ....    also see Help>Price Level List