You're right, profit tops out well before you get to "big money," usually due to limits on either supply or time. In the used clothes example you are either li

You're right, profit tops out well before you get to "big money," usually due to limits on either supply or time. In the used clothes example you are either limited by time (I can only hit ten thrift stores in a week) or supply (there are only ten thrift stores in my area.) After that, how do you scale up?