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?
I would say that the general answer to your specific question is no. If you want to justify buying a printer because of all the things you could print instead of buying that is not going to be easy.
If however you are a DIYer and you have some CAD skills, or are willing to learn some, then consider the 3D printer as another tool you can use. There are plenty of stories about people who fixed some very expensive thing instead of having to buy a whole new one for hundreds of $/£; so if you have a specific use in mind then it may be justifiable to you.
I have made and fixed stuff around the house, but it's often things you simply couldn't buy, or could have fixed some other way.
There is an ever growing library of models available out there, and many are free. I recently fixed the leg on my keyboard with a printed one which I found on thingiverse, took minutes to print and the keyboard is part of a wireless set which would cost £30 to replace, so that was great but you won't normally find exactly what you want like that at this time.
And lastly it's not plug 'n Play yet, so you need to be a tinkerer at heart to use most printers out there right now.
You'll never net a profit 3D printing the equivalent of Dollar Store trinkets. Commercial-scale injection molding costs pennies per part, while 3D printing typically costs dollars per part. It's great every so often when you can replace an out-of-stock widget and rescue a major appliance from the trash heap, but those instances are pretty rare.
What 3D printing lets you do is make stuff that simply wouldn't exist otherwise. That could mean clever gadgets that can't be manufactured any other way, or niche items that don't have enough volume to be economical via traditional manufacturing and sales channels, or one-off prototypes or art projects. Those may be very high value items! But it's difficult to assign a dollar value to them.
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.
What 3D printing or additive manufacturing is good for is printing small and delicate stuffs. examples: scaffolds, tissues, human organ. i've seen some people use 3D printing to print bone or a part of it.
Also, it's good for fast prototyping, especially you don't want to wait for the machine shop forever. that's where 3D printing comes in.
What is not good about 3D printing is the piece cannot withstand normal force/stress as compared to regular casting/manufacturing ways. 3D printed work piece are easy to break compared to other methods. no matter what alloys/plastic ink you use, there is always something better. 3D printing don't give the best. as such, manufacturing still relies on old methods.
let's review the pros and cons of regular manufacturing (mfg) and 3D printing:
+cost: design mold, more time/money investment to make equipment
+profit: faster+cheaper (in term of $/product) for mass production
+cost: cheaper machine (usually but not always, depending on the input materials, could be alloys, plastics, etc.), laser type (diff commercial printers use diff laser)
+profit: cut time to make equipments because it's ready avail, more expensive but also more control so each of these methods have their goods and bads. personally i think it's usually worse than better compared to regular mfg so it doesn't make much sense to me.
So in my opinion, no.
