there are several issues with your reply. First, please show us where on amazon's site you can currently order any of the new mba configurations with 4gb of ram -- and by that, i mean items that are actually available for sale and not listed as "unavailable" (with no indication of when/if stock will be resupplied) or backordered.
Second, being in california does matter. You mention both macmall and onsale as buying options. Did you know that the latter is a subsidiary of the former? And, furthermore, that macmall (which is, itself, a subsidiary of pcmall) is based in southern california, which means that sales tax of almost 10% will be applied. This makes buying from macmall/onsale no different than buying from the apple store, except that with the latter you have less hassle with respect to exchanges or returns if something is wrong.
So, again, you provide amazon as an option, but there aren't any 4gb config's available at the moment -- there were a few days ago, but the seller was not amazon but, coincidentally, onsale, which would assess tax on the purchase. And you also suggest macmall and onsale which also assess sales tax, contrary to what the op was inquiring about.
I believe the op's concern is valid. As a ca resident, opting for a base 2gb model of the 11" mba, as in my case, costs quite a bit less than configuring one through apple, macmall, or onsale. I should mention that there are two other options that don't assess tax for ca residents: Macconnection and small dog.
