In centralized world, Buyer usually surfs the web, then goes to Seller's web-site, study various pages, somehow get pricing via site or by contacting sales. Then, he register's on web-site and sets a password, that will be used to consume a service. Afterwards he downloads a client software, that has preconfigured addresses of servers, various software settings. He logs-in using credentials, he has set up previously. If it is a web-service, he consume service via browser, but still need to understand terms and pricing and setup credentials. Looks not so complicated, but still terms and process are always custom for each provider.