Just like the hotels I would imagine they get them at knockdown prices. After all, most of them are just ordinary products tarted up with fancy labels and names.
I remember Esther Rantzen had some of these overpriced creams and potions analysed and found they contained more or less the same formulas with the odd stupid ingredient thrown in for good measure to make them different from the cheap ones.
You can make your own for pennies using items in the kitchen larder or under the sink.