that is why i said "one site." +ebay +amazon +every scalper site +ticketmaster auction +etc........
chances are scalpers list tickets on more than one site, thus you can't do a simple addition of all the sites... you'd be double-counting.
and sorry, i went back to stubhub. there are 1000 lawn seats available.
this news should make you happy: i'm not convinced scalpers will be able to sell that many tickets at those high prices. i wouldn't be surprised if you saw a bunch of cheap tickets appear in the week before the show.
and if merriweather lawn can hold 10000+, how does ticketmaster process that many orders in one minute?
distributed computing, server farms with hundreds machines, high-speed networking... it can be done. also, the entire order doesn't have to be processed before the show is shown as "sold out", the tickets only have to be reserved - that's the first screen after the captcha, where you're shown what seats the system is offering you. that's a simple database hit, not very computer-intensive. pulling up your account/entering your billing info and the credit card processing, that takes time - but the show can be sold out before then, since the tickets are taken out of the available inventory pool.