Depends where exactly you are, I'd wager 50% of them are currently officially "take it as deposit or as buying" because they're often styled for the specific christmas market and vary from year to year. Not sure why people would collect those, but to each their own.

Yeah, but the deposit is higher than the retail price.

that's the right price to set it at... just more expensive that it would cost to buy the mug from a mug store rather than a coffee store.