On the documentation page of "Create a console app", the following line is present
"Salesforce console Available in: Enterprise and Unlimited Editions with the Sales Cloud for an extra cost"
My question is; where can I purchase a possibility to create console apps?
You should contact your account executive to discuss getting the right license in order to get access to the Salesforce Console, as it will depend on if you've currently got a Sales Cloud vs. Service Cloud license.
If you aren't sure who your AE is you can call or use the live chat from Salesforce.com and a support agent should be able to help you get that information.
You can find more information about various editions and feature licensing here http://www.salesforce.com/crm/editions-pricing.jsp
