I found out about the Mr. Olympia expo back in 2009, and every year in September I make the 3+ hour drive to Vegas for a typical fun weekend & to come up on about 4 months worth of free workout supplements.
As far as that one negative review claiming they got charged $35 for tickets at the door I'm going to have to call BS. Every year I've been to this expo I got my tickets at the door & the price was as advertise at $20 or $25, as far as what kids get charged I don't know.
A few tips for the expo, bring an empty back pack, you'll need it after an hour of so to split up all the free stuff you got & to drop some of the weight out of the bags that you have. Parking, usually during this weekend I stay at the Rivera since it's one of the cheapest hotel on the strip, & it's also the closest to the expo besides LVH which is the hotel that host the olympia expo in their convention. The parking tower for the Rivera is free so I usually walk 5 minutes across the street instead of paying $10 or $15 to park my car in the sun. Last tip if you plan to go on Sunday go early take a break then go back an hour or two before the expo closes. Sometimes the vendors still have samples they get rid of & will give out more just so they don't have to pay to ship them back & the same goes for the vendors selling items, sometimes they offer better discounts than they did earlier in the week just so they don't have to take extra stuff back with them.