My own experience earlier this month: $50 (fifty) hold for 4 nights in Los Angeles: The Andaz West Hollywood hotel, a couple of weeks ago. Minibar is complimentary only for non alcoholic beverages there, also there were 3 bottles not in the minibar well worth more than $50 plus other valuables in the room (for example two interesting books on the history of the Sunset Strip and Hollywood in general). I had booked the room via Priceline, I think I paid $470 for the whole stay (w/taxes). I didn't touch anything, only the complimentary water and tea.

Now those charges are gone.

Since they get your credit card number, I think they can charge as much as they want, if -and only if- after your stay they find out you drunk their alcohol or done some kind of damage to the property. But $500 in advance is way too much, in my opinion.