Dollar store shopping: bargain or marketing ploy?

According to a recent Nielsen survey, savvy recessionistas now shop at dollar stores. Wanting to be savvy, I journeyed to the nearest Dollar Tree, which makes me sound like a character in a fairy tale:

"And there, Marco the Scribe found a magnificent tree and it was blooming money..."

My initial impression was to be impressed at how much you could buy for a buck: a shower curtain, a dog dish, safety goggles, a soap dispenser. "How can these stores stay in business?" I thought.