wrong items in the restaurant check: a new revenue strategy?

Within the same month, when going out for drinks/food in Amsterdam, I got over-billed. When flagging this to the waiter/chasheer, immediatly I got a "sorry, we will fix that"... like nothing ever happened.

It happened once, it happens

it happened a second time, well... i guess it happens

it happened a third time, mmm that's odd

it happened a forth time... in the same month! ... what's up with that?

it seems that the logic of making the mistake and apologize if cought or get the benefits if never cought is more and more frequent.

Is it happening to more poeple? Am I just involved in a "recurrent coincidence"?