Stayed at Sheraton Lisbon in late Nov'07. The hotel was still undergoing renovations to its fitness center and parking facilities. Thus, the valets were parking the cars out front for free.

Now, that the renovations are most likely complete, it is probably back to what I would guess 15-20 euros or so per day. I also remember reading somebody's post in the older threads mentioning that Plats were comped the parking. Better e-mail the hotel to find out about the current situation.