We’ve noticed that a few tour bus companies in Ushuaia, running between the town and the national park, will offer us a discount (say 55 pesos round trip for what they say is normally 70 pesos), but then write the original full price (70 pesos) on the receipt and ticket. Why would they do that?

I’m familiar with various schemes where someone charges you a high price and then documents a lower price (maybe they pay tax on the documented price, maybe you pay duty or tax on the documented price, maybe they’re working on a basis where they have to give X% of the documented price to whoever owns the taxi or bus or stand or what have you — in any of these cases, it’s to their advantage to hide some of the money they’re making). What’s happening here is the opposite, and I’m curious what the angle is.

Maybe they’re not officially allowed to compete on price — there’s a set price for all bus companies, and nobody’s supposed to undercut it to attract customers — but they do anyway, and don’t want written record of that?