Don't discount the factory mats. They've been very hard wearing, even if they are a bit pricey. But you can routinely score a deal on them via eBay. And there is a seller in SoCal who has a set on the local Craigslist for only $60, which is a bargain indeed:
http://losangeles.craigslist.org/lac/pts/3050193339.html" onclick="window.open(this.href);return false;
But one thing I can tell you...you don't want to go without, for ANY length of time - the factory carpets will pill in no time at all. And you don't want to go without for the rear if you have anyone back there in a regular basis, for the same reason.