Astronomical bills while on vacation

Whenever my sims go on vacation, within one or two days of arrival they receive a bill for an astonishingly huge amount of money, which bears no relationship to their normal bills at home and/or the cost of renting their holiday accommodation. This is happening irrespective of whether they are in Selvadorada, or in Granite Falls. The latest bill my sims received was for over 80 000 simoleans, which was a real shocker. Fortunately, these sims are very rich indeed, so they could afford to pay it, but surely this is not right?

Is this happening to anyone else, or is it only me? I have LittleMissSam's auto-pay-bills mod, so that might be one possible cause, but I don't want to remove my (very few) mods if the problem is with the game itself. Can anyone throw any light on the subject?