Hi
I use a Lulzbot TAZ6 to print my parts.
As you have noticed, using 3Dhubs to print your parts does get quite costly depending on your choice of materials and 3D printing processes.
3D printed parts, under compression do quite well.
Since my TAZ6 is FDM process, I’ll go there.
When 3d parts are printed using FDM process, there is a grain to the parts.
They are sort of built like Plywood.
Strength characteristics are very similar to Plywood.
If I need maximum plastic strength from my parts, I’ll print them so they are oriented for maximum strength and glue them together.
When I make a maximum strength part, Its usually a glued together assembly.
When oriented properly, 3D printed parts are quite strong and durable.
I’m being a bit vague but, more than likely you’ve experienced the plywood effect.
Sometimes reinforcing the grain of the part using a piece of filament or designing parts that glue together good are the answer to strength.
I think the parts I design, keeping the grain in mind, gives me very good results.
Most of my projects are printed in ABS or Nylon and I’ve had very few failures.
I hope my ramblings here have helped you in some manner.