Poor people pay rent.
Poor people buy food.
Poor people pay for transportation to and from their jobs.
Poor people also pay for substances and activities that can distract them from the realities of their situation for a short time.
The employers (rich) set the wages at a level that barely covers the cost of the goods and services needed by the workers (poor) to survive day to day. Preventing them from collecting sufficient means to rise out of their situation.
Just because the people of earth are poor, doesn't mean they don't have a lot of money to spend. If an earth person makes $75,000 a year, and it costs that person $74,500 to get to and from work, eat, clothe him/herself and pay for shelter, that person is still poor. More so if the cost is higher than what they can earn.
It's not just products that make people rich. Food, shelter, transportation. These are things people need everyday, and can earn you a lot of profit.