i took a tour there last year with sunset tours out of vegas. it left around 7am i believe, or we had to be there that early, i forget. but they picked us up from our hotel in a limo to bring us there.
the price was like $380 a person i think.
however, we had a hiccup in our trip...
when we got there it had been raining, and it started to rain during the helicopter tour. and literally as we were flying over the wall to get into the grand canyon, it looked like the perfect storm that we were flying right into. so we had to make a uturn and head back.
the good thing was, they refunded us 100% of the money. so we basically got a 90 minute helicopter ride for free over lake meade and the hoover damn. it was still a cool experience, and i wish we could have gone into the grand canyon to get out and stuff, but safety came first. we couldn't reschedule either because of the time left that we had. but they were really good about refunds, and actually gave EVERYONE a refund. there were like 4 or 5 helicopters full of 4-5 people in each. that is a lot of money they lost, but part of the business.
word of advice - ask if you can sit in the front. they sit people based on weight distribution, and i asked about sitting up front when i called and booked. and thankfully they let my wife and i sit up front. sitting on the right side where the door is in the front was awesome, because you have like a bubble door that wraps around, and you can see below you a bit. the people in the back, especially the middle, probably saw a lot less than i did.
definitely an awesome experience, and my wife and i already said, next time we go to vegas, we're going to do it again and make it to the grand canyon.