Actually I have found that to be a terrible way to figure out prices. The reason I say that is this: Artists and performers are generally very bad at judging their own worth. I have a simple theory as to why this is: What we do is fun, and it's hard to consider something fun to be work. So we undercut ourselves.
Jamie Grant has a great essay on how to set up your fees. If you search "Jamie Grant How Much To Charge" you'll probably be able to find it. It's geared toward walk around performers, but it gives you a decent frame work in general.
What I also recommend is finding out what other performers in your area charge and using that as a guideline as well.
It is vital to remember what you're actually charging for as well. It's not the 45 minutes you're on stage, said and done. It's also the hours upon hours you have (hopefully) spent rehearsing your show, any consumable items (flash paper, playing cards, etc), the expense of transporting yourself to and from the gig, etc.
So! Let's math a bit.
Say you charge $100 for an hour long show. The show is 30 minutes away. It takes you 30 minutes to properly set up, and 30 minutes to properly break down. The numbers I'm using are for simple maths, btw. That means this show actually involves an hour's worth of transport, an hour's worth of setup and break down, and then an hour's worth of performance. 3 hours. Suddenly you're only making $30 an hour. Personally, when I'm performing, I rehearse my show twice a day, every day. So let's take just the week of that performance. 7 days, by 2 runs of the show each day is 14 hours. So now we're up to 17 hours of work, for $100. That's $5.88/hour.
Now it starts to make a lot more sense when you see the guys who are charging several hundred per show.
