I also noticed that Czech Harem clip the other day...it probably is the ultimate male fantasy.
I've had an 8-some with 7 girls at the end of a party once...tbh it was a bit overwhelming (but in a nice way). I had already cum so wasn't in my prime to take advantage fully, but to have all those pretty faces and boobs surrounding you, a pussy in your face while another girl is sucking you, another stroking your balls, one on each nipple and a chorus of ooohs and aahs willing you on 'cum for us big boy!' was something I won't forget 'til the day I die!
I reckon you could 90% of the Harem experience at a 2hr+ 2:1 ratio party in that you can get round a good number of girls, with some sort of action available pretty constantly and you may get a bit of moresome action, but of course it won't be your personal harem, that will cost you big time. But personally, I'd rather do 10 parties than blow £1500 on a reverse gangbang, where the majority of the girls are going to be idle most of the time...no way you're ever going to fully pleasure them all...but certainly one to bear in mind for a lottery win!