Mojang does not sell Minecon capes.
MINECON 2015 Capes
When you arrive at MINECON, we'll scan your ticket, and only scanned tickets will get a cape. Tickets that are not scanned at the event will not get a cape. The capes will be sent out as a redemption URL to the email address used when purchasing the tickets, if you have bought more than one ticket you will get all the redemption URLs in one email.
Previous Years' Capes
In 2011, capes were automatically attached to ticket-holders' registered usernames.
In 2012, a message was sent to the registered email address containing a link that would allow for the addition of a cape to the user's profile. If an email was not registered, the message was sent to the email linked to the purchase of the tickets.
In 2013, capes were sent as a redemption URL to the email address registered when the ticket was purchased. If someone else purchased the ticket, please contact them for the cape redemption link. Mojang Support cannot resend cape links or give them to another person.
Mojang Support is no longer adding previous years' capes to accounts. Cape activation links do not expire.
If you have more than one type of cape, you can switch which cape you are wearing at minecraft.net/profile.
We do not transfer capes between accounts.
For information on other cape types, visit the Minecraft Wiki.