A station with 30,000 people would have multiple bulk food stores, whole shopping malls, factories, you name it!!!

Imagine a space station with artificial gravity, and products that people would start to manufacture in support of their lifestyle. Toys for kids that exploit the variations in gravity and coriolis effects. Hospital equipment for fractional gravity environments, all sorts of robotics and new computer algorithms for dealing with navigation on cylindrical surfaces, and flying through air with coriolis-induced air currents. Personal hygene products that can cope with people's needs in space, fashion statements & preferences may be quite different.

Safety systems! Just imagine the products people would buy, the ideas that would swirl with the first-hand feedback from so many people!

Tourism might be a primary industry. Wages earned from catering to the millions of potential tourists would be spent in the shops and malls throughout the station. Permanent employees might save some of their money for their vacation to earth, or invest in new space ventures, like buying shares in a lunar mining robotics company, or an orbital solar powerplant, or in additional Skyhooks that will earn revenue through fares paid by the passengers. Or maybe they will prefer to pay for satellite tv, piped into their condo in the sky, broadband wireless internet, or instant messaging to their family earthside.

Once you have sufficient numbers of people, the trade and commerce begins. But without people there is nothing of any sort. Do you think 3 people would be considered "consumers". I think not. Perhaps 30,000 crew, yes.