Why Customers Who 'Already Know What's Wrong' Pay More: A Field Experiment Inside the Repair Market

Every shop owner knows the customer who walks in certain they've cracked the case. "It's the compressor, I looked it up." You'd think handing the tech a diagnosis would speed things along and maybe shave the bill. A natural field experiment in the repair market found the opposite. Customers who told the technician what they thought was wrong paid more, not less, and the ones who guessed wrong got hammered.

The study, run by Rudolf Kerschbamer, Daniel Neururer, and Matthias Sutter and published in the Journal of Public Economics, sent undercover customers into computer-repair shops with an identical, minor fault. Some said nothing about the cause. Some offered a correct self-diagnosis. Some offered an incorrect one. Same broken machine, different scripts.

Here's what came back. A correct self-diagnosis did not earn a lower price. And an incorrect self-diagnosis more than doubled the bill. Telling the tech "I think it's X" when it isn't opened the door to a much larger invoice.

That's not a story about crooked technicians. It's a story about the kind of market repair is.

Repair Is a Credence Good, and That Changes the Pricing Math

Economists call appliance and HVAC repair a credence good. The seller knows more than the buyer about what the machine actually needs, and the buyer often can't verify the diagnosis even after paying. You can't see whether the board really needed replacing. You trust that it did.

In that setup, a customer's own words become information the shop can act on. When someone announces an incorrect diagnosis, they've signaled two things: they don't actually know what's wrong, and they've anchored themselves to an expensive-sounding fix. A shop inclined to oversell now has cover. The customer asked for it, more or less.

The honest shop faces the mirror image of the problem. When you correctly tell a walk-in that their $600 "compressor" is really a $90 relay, you've just talked yourself out of revenue, and the customer has no easy way to know you did them a favor. That asymmetry is exactly why credence-goods markets punish honesty unless something rewards it from outside.

The Thing That Rewards Honest Shops: Real Reviews

The study didn't stop at the counter. It also looked at whether online information helped customers protect themselves, and here the finding is genuinely useful for owners.

Customers who consulted a platform's algorithmically recommended reviews (the study used the reviews Yelp actively surfaces, not the ones it filters out) were better able to find fair-priced, quality shops. The reviews the platform chose not to recommend were misleading. In other words, the filtering did work, and vetted reputation steered buyers toward the shops that deserved the business.

For an owner, that's the practical hook. The same information asymmetry that lets bad actors overcharge is the thing a strong, genuine review profile cuts through. You can't easily prove your diagnosis was honest on any single job. A stack of real, recommended reviews is how the market figures it out over time. That's worth building deliberately, which is the whole point of a real Google review strategy for a repair business.

It also shapes how you quote. A customer who trusts you doesn't need to armor up with a wrong self-diagnosis, and you don't need to price defensively against one. Clear, consistent pricing does more than protect a margin; it removes the guessing game. If you've never sat down with the tradeoffs, our breakdown of flat-rate versus time-and-materials pricing is a good place to start.

The lesson from the data isn't cynical. It's that repair runs on trust because customers can't verify the work, the confident-but-wrong customer is the one most likely to overpay, and the shops that win long-term are the ones a real review platform can vouch for. Build for that, and the "I already know it's the compressor" crowd becomes an opportunity to prove you're different, not a temptation to cash in.

Sources

Kerschbamer, R., Neururer, D., Sutter, M. (2023). "Credence goods markets, online information and repair prices: A natural field experiment." Journal of Public Economics, Vol. 222. https://doi.org/10.1016/j.jpubeco.2023.104891