I think about it as business to consumer versus business to business. B2C is about status. B2B is about lasting relationships. By default, anyone searching for services on freelance aggregators is using a B2C model. Status can be about spending lots of money, but it defaults to being a saavy shopper or hard negotiator and such. Basically people with a B2B view of web design and lots of projects already have a relationship with a design provider.