The tricky part isn't making the website, it's persuading enough people on both sides of the equation that your business is a better option compared to alternatives.

And despite the situation with Ticketmaster it's not like they're literally the only tool available in a market waiting for a second option - there's already lots of much smaller ticket-selling options that you'd be competing with, ranging from single person PHP websites you can host yourself to companies with significant traction in their niches that are like Ticketmaster just much, much smaller.

That's not to say that an idea like yours couldn't succeed, but the fact that lots of people could do the coding doesn't make it a likely, or easy, business to make successful.