Any question that involves cost needs to consider TCO - Total Cost of Ownership.

This means you do not look at just the price of something, but all the costs needed to run it and use it over long periods of time.

First for the copy shop

What do they charge per page? What do they charge for colour pages? Do you print in colour? How far is the copy shop from you? How often do you need to go? Are they open 24/7? Can you get there anytime you need to? How much does it cost you to go? (gas, bus pass, subway, taxi, etc). How much time do you need to go there and back home? How convenient is it?

All of the above questions have a value assigned to them. Especially the time and convenience type questions.

Now for an in-home printer you would calculate things like initial cost of the printer (this will vary on your requirements, do you need colour? do you need scan/fax capability?, etc), how much does replacement ink/toner cost? How fast will you need to replace ink/toner? What is the cost of paper? How fast will you need to buy more? Even something as small as what is your electrical cost to run this printer and where can I put it (this is a bit overkill for most people since electrical is miniscule for most printers and home users really aren't worried about giving up space for a printer and what that "costs" them).

All of these factors (and more) play a part in TCO.

For me, I always buy a home printer simply because I hate the inconvenience of having to go to copy shop, having to go when they are open (so its on their schedule not mine) and the drive there and back and gas and everything else lol.

For me those factors weigh heavily as a cost analysis and so I always end up putting more money up front and buying my own printer.

If your printer lasts a few years (so you can't buy the ones on sale for $29 USD) you will definitely save money in the long run over a copy shop, plus your time and convenience.