I rented a car recently for $12 a day.

The week before the same model was listed at a daily rate of $22.

I just went online and the price is now $10.95.

It is impossible anymore to know what things are supposed to cost. I can’t decide how I feel about the trend.

I mean, I like a deal as much as the next guy, but I hate finding out that I might have saved even more if I just read one more paper, opened one more envelope or visited one more Web site.

Does dynamic pricing build or defeat brand or store loyalty?

I sometimes watch the new extreme couponing cable shows for tips on securing the best deal. My favorite so far? One woman put her young children to work clipping and coordinating coupons — she “managed” the process.

If only I could delegate the chore.

Instead, I see things come home that I know could have been had for less.

“I have a coupon for that,” I mutter, only to be met with a shrug. Convenience has trumped value.

My calculus tends to work in the other direction. I sometimes find myself unable to make a purchase, paralyzed by the conviction that there has to be a better price somewhere. I’m the guy who pulls out a smartphone and punches in serial numbers to compare prices at other retailers.

The last time I tried that, my son rolled his eyes and headed for a distant corner of the store.

I blame the economy for all this pricing uncertainty. There is inventory to move, and tightfisted customers to acquire. Like me. There was a time when my weekly grocery errand involved making stops at no fewer than four stores, all offering an different assortment of discounts.

I’ve since found a better use of my time, even if I have not entirely licked my addiction.

So I realized when I saw an ad for Papa Johns last week — $10 for a large pie with pepperoni and a double portion of spicy Italian sausage. No, wait, somewhere at home I had a coupon promising two larges for that same price. And then, eu­reka, I found the ultimate angst-ending offer: The Washington Post’s Capitol Deal site sent me an e-mail giving away a large Papa with one topping, for free.