I agree a lot with your hypothesis. Most people in my demographic (mid 30s American) that aren't having kids are choosing not to primarily because they don't want to really interfere with their current lifestyle. Money seems to be a part of it, but secondary to the high opportunity cost of children.

There are also social effects. When half your friends have kids and half don't, you can compare the lives of each and decide which you want to live. You won't be as isolated now if you choose not to have kids... in fact the trend seems to be that having children is the isolating choice.