If you already have a 3D printer, would you say that you have saved money on buying the printer, buying models and then printing the models, compared to buying something alike in retail?
Would you say that saving money is an argument to buy a 3D printer?
Yes and No.
There are two sides of this, yes and no. Why I say yes is because there are little things that the 3D Printer can come in use for, like creating charger holders or just little household objects. The no side of this for me would be because of the cost of the filament in general and the maximum object size you can create with your 3D Printer. I know they have bigger ones out there, but you aren't going to make anything too big. Another reason it's a no is because of duration of time. It may save you money, but your going to be spending a lot more time and possibly more money the bigger your objects get, which is the only reason I'm not trying to get one at the moment. I'm choosing to wait until technologies advance to get my personal one, where it doesn't take over an hour to print out a keychain tag.
So yes, you probably could save money in the long run, depending on what you create with it based on size and how much filament you use, but I'm also going to say no because of the disadvantages the 3D Printer has. I personally would wait for technology to advance in the next 5-15 years before buying one that has a lot more power than these, as the one's currently in the market are expensive.
EDIT: As I stated in my reasoning, I currently do not own a 3D Printer, but I do use one at my school for educational purposes and I do know the hassle on time and money for creating products that are relatively small in size.