http://www.cirquedusoleil.com/CirqueDuSoleil/en/default.htm
They have five shows in Vegas. LOVE is the one I prefer as Beatles fan.
You can try to find last minute/same day tickets in Vegas for 50%. But it all depends on your luck. For some of hte popular shows, the tickets are sold out weeks before the date.
If you visit Vegas in the middle of the week it is easier.
There are five ticket offices from two companies offering the same day/50% off tickets and I think you can google them.