I can agree that it won’t be worth it to use 3D printing for mass production since The time that it takes to make every single piece will be to much. However I think that printing is the optimal way to make a prototype since you won’t have to pay for tooling to make them before you have seen the object in real life (quite a difference from the computer screen).
If you print a prototype to have some printing on I would recommend you to find someone who could print it in one piece. If there is a need for shipping, this will be more expensive, but you will save a lot of time trying to get the seams good enough if you want to print on them. I could probably do that but since I’m on the wrong side of the pond shipping will probably be a bit more expensive compared to if you find someone local (I think about 50-70 usd).
For mass production I think that The best way to do it would be vacuum forming two halves and fusing them together with heat or solvents. I have worked with a company before who does this and the finished products came out beautiful, with printings on them.
