So I can't speak for all conditions, but cubesats do not usually ride for free. The prices I've seen are usually in the 50k / unit range. So if you've got a 1U cubesat, expect to spend at least 50k on launch. Part of the reason for this is that there are integration costs for attaching a cubesat deployer to an existing launch vehicle, as well as liability risks, control and thrust timing modifications etc.