The cost of plastic in 3D printing is virtually nil, the real costs are the design and print times. If you do your own design, you control those costs, and, if you have your own printer, the printing runs unattended so, if you have an UPS to keep it running during brief power outages and can leave it running for as long as it takes, you can make literally anything.
The attached photos are of a prototype of a drip valve, printed in PLA, at a total plastic cost of $0.33 (approximately 1.2Meters from a 1KG spool that cost $25 and contains 880 Meters of filament). I don't recall exactly how long it took to print, but I believe all 5 parts took a total of about 3 hours and can be printed in a single run (actually there is room on my printer bed for probably 4-6 sets of parts).
You don't need ABS unless the piece is going to be exposed to a harsh environment (temperature or high humidity) and I haven't used ABS yet since I don't have an effective means to filter/vent the styrene fumes - yet. I can print PLA in my office unvented...
Tom