We have a similar problem in research, where we have to always demonstrate that what we do is novel. A technique that I have taken a liking to is to talk about all of the related work as soon as possible, so we can distinguish ourselves immediately. The difficulty with only distinguishing yourself at the end is that your audience has been bearing a "someone has already done this" grudge the whole time. It's difficult for them to let that go, no matter how good your answer is.
edit: I just looked at the page for your startup, and it wasn't immediately obvious to me that your site is a place to find classes out in the real world.
Yes and no. I'd maybe try to rephrase that to something along the lines of "I've looked through their site and I haven't seen any evidence of them attracting users". Dismissing a rival with "meh, no-one uses it!" makes it sound like you haven't really considered the competition.
And if you don't have a list of damned good reasons why no one uses X, then they shouldn't give you any money.
BTW, I don't waste too much time concerning their success (just a once a month check) especially since my company's success is most important. No one asks "Isn't your company just like X" when you are winning :)
A really simple graphical explanation about who pays what might work? I really don't know, but what does peak my interest is that it seems like it will be a variety of crazy stuff rather than another lesson in math.
I liked the comment that you should start your pitch with what others are doing and how you will address a different market or beat them in their own market.
This stuff is obviously really tricky, but I feel like you have something you just are not showing.