It’s a question that shoppers get asked a lot — by car dealers, electronics salespeople, even at the toy store: Do you want to purchase an extended warranty with that?

With post-holiday sales well under way, this is as good a time as any to answer that question.

Generally speaking, extended service contracts are major money spinners for retailers; that’s why they push them so aggressively. Many people never use them, or forget they have them, or are frustrated to learn that their particular problem isn’t covered.

And generally speaking, most products already have a manufacturer’s warranty covering at least the first year of use (when bad things typically go bad) and are designed to last long enough to give you your money’s worth.

“If the merchandise costs less than $100, it’s probably not worth having an extra service contract,” said George Whalin, a Carlsbad, Calif.-based retail consultant. “But if the item costs more and is relatively complex, you might want to consider it.”

He offered his own experience as an example. Whalin said he purchased a fancy flat-panel TV, and almost as soon as the manufacturer’s warranty had expired, some component inside went kerblooey.

“A service call would have cost a fortune,” he said. “But because I had an extended service plan, I was OK.”

So there you have it. Or not.

“I completely disagree,” said Mark Kotkin, director of survey research for Consumer Reports, the publication that tests and rates thousands of items. “Even for an expensive TV set, the cost of repairs can be reasonable, and flat-panel TVs are generally reliable.”

He said data amassed by his organization show that the cost of the typical extended warranty for various products is about the same as the cost of the typical repair.

Because most products are either covered by the manufacturer’s warranty or simply don’t break down, Kotkin said it’s usually wiser to pocket your cash and play the odds.

For example, the median extended warranty for a laptop computer was $200 as of a few years ago, according to Consumer Reports. The median repair was $200. The median extended service plan for an electric clothes dryer was $125. The median repair was $120.

Both Kotkin and Whalin said businesses push extended warranties on customers because they make tons of money from them. Profit margins for service plans run as high as 80 percent, they said.