Years back DP and I had a weekend away with 3 other couples. Lovely spacious rented house a couple of hours drive away, we divvied up what we would need in terms of food and drink as we were self catering every meal. Everyone brought their fair share and shared the cooking. Great weekend, not expensive and something we were keen to repeat.
One couple said that they'd raved about the weekend to his parents and they'd offered us the use of their holiday home for the next one. Although it was considerably further away we thanked them and started to plan on the same principle as before.
The couple then sent out a message to say that they were going to stay there the week before so they would organise the food and we could split the bill when we got there.
We arrived to find that it was much smaller than we'd been led to believe. We had all brought wine and nibbles. The couple then announced that we had to have a meal out at a specific unmissable pub. Not what we were expecting but ok. The couple kept putting off telling us how much we owed them but the food they had bought was all the opposite of what we had done previously. (E.g. instead of own brand cornflakes it was Waitrose croissants, a range of bonne maman preserves, President butter).
We discussed away from the host couple what we could do for their parents for the loan of the cottage. The general feeling was that our own parents would be happy with some nice wine in the same situation so we bought a case to leave at the cottage for their next visit. (The cottage wasn't let out when they weren't there so safe to leave it)
As we were packing to go home at the end of the weekend the host couple came to us all individually and said that they thought their parents would like a piece of furniture as a thank you which the couple had ordered on our behalf. They then told us how much we owed them for the weekend which turned out to be 3x the cost of the previous weekend without the additional travel costs and the meal out.
Stupidly we all felt we had no alternative than to pay and we had already given them the case of wine. We never went away with them again even though they kept pressing us to join them at the cottage for a long time afterwards.