If you plan to keep the car for a long time, then the cheapest shocks you can buy are also the BEST: Bilstein monotube shocks and struts, baby! Sure, the up-front cost is pretty high, but you'll never need to replace them. Ever.
KYB makes some very good performance shocks and struts, but nobody makes 'em like Bilstein. Besides, you probably won't be getting monotubes if you get KYBs. The monotube design is worth its weight in gold. They are naturally progressive, without a lot of complicated valving. They are impervious to cavitation. ("Fade.") And, though the design is dead simple, it requires the absolute BEST in materials and workmanship in order to be reliable. Monotubes are made with very thick, heavy-duty, machined shock bodies. Internal tolerances are far smaller than anything inside your engine. If they aren't built like surgical instruments, they won't work.
Gabriel and Monroe build crap. The only time I'd buy them is if I need to add new shocks to sell a car to some poor sap.
I suppose one could make the argument that a Gabriel or Monroe is "cheaper" if you can get a lifetime warranty. I guess it all depends on your tolerance for crawling under your car and replacing shocks every year or two, and dealing with mediocre performance in-between. I have a very low tolerance for grovelling under cars, and I HATE floaty, poorly-damped shocks.
-mickey