Now THIS would make a good 3D printed part
I would agree with you . . . almost.
I purchased a 3D printer, in order to make replacements for my wagon (among other things).
A 3D printer does a decent job to make a prototype to then use as a mold for injection moldings - but is not quite good enough for production sales.
For one-and-done parts, it can be good enough.
3D printers need a good and preferably long flat surface for your print job to stick to the printer bed. I have one of the broken belt covers by my computer right by my and there is not a good flat surface there to make a print from. The curved side (edge) almost can be used - but even then, you will need to do some filing/sanding to get the edge closest to printer bed, back to a rounded edge.
Of the parts to use for 3D printing, that belt cover is just not very compatible.
BudW
Edit: next, is you need to make a 3-D picture of the part for printer to make prints from, and that is another hurdle to leap. Once you have the 3D file, you then need to convert it do something the printer can actually use, which in the case of my 3D printer is ".gcode" (which is also used for abrasive water cutting, and other computer controlled machines that use that kind of programming). Converting to ".gcode" is not that hard to do.
Getting an decent 3-D picture is different story.