Why are you being so defensive? I don't believe anyone in here was talking to you like you are an idiot. They simply answered the question you posted. Yes I see your point, you are right it would be a lot cheaper to make one as opposed to buy one but not everyone has the time nor skills to make one.
I have the skills to make one but time isn't something I have to put into a rack for my snakes so I bought a couple or racks. It just depends on what you value more, I for example would rather get off work spend time with my family or hit the gym than put time into making a rack, so in turn I'll spend more for a built rack.
If you have the time and skills to make one by all means go ahead that's great. As for the car/mechanic thing I'm sure she meant it as a skills thing. She doesn't how to fix a car so she could a) read about fixing and attempt herself or b) save the time and get it done right so take it to a professional. That's all they meant from what I took from it, not comparing cars and racks.