Well, scavenged parts can be cheap if you know what you need and where to find it.
I do not have a clue yet what I would need to build my own 3d printer, but I did just buy 2 all in one scanner/printers a couple days ago for $5 each!
So I got precision rods and motors and belts and whatever else I could use from 2 scanners and 2 printers for $10 total!
Actually these units do still work well, but they need ink which for the average user costs MORE than a new printer! LOL
I know the costs as my daughter needed ink for her printer while I was visiting her and all new ink for the Epson would have been about $100 and I could bought her a new Epson printer for $70!
Since her printer uses the same ink tanks as mine I just bought her the 1 black she needed to print for now ($20! ) and will mail her some of my extra tanks since I do not use them. I use special inks and a continuous ink systems so never opened the ink tanks for my 4 printers.

Anyway, my point in general is parts may be cheap or even FREE. I could have had 2 other printers Free just to take them away, but I was 600 miles from home and could only carry back so much junk LOL I only bought the 2 $5 units because I can use them with refill tanks I already have to make coffee mugs and such imprinted items.
I had not thought of using the parts at the time to build a 3d printer or a router table etc.. or I would have got all the $2-$5 and FREE printers and scanners and just took a night to scrap them out for parts and tossed the big stuff like the cases!

Check Thrift shops! I check all I can anytime I can and when out of town at new places! You never know what you may find dirt cheap and sometimes free! I consider it fun thrift shopping, not because I can't afford new things, but because I gets tons of stuff for projects I would never buy otherwise!
I bought 2 good sized Pressure Cookers for $3 each and not a thing wrong with them! I may keep them for cooking or use them for boilers for model steam engines that will run on 10psi.
I got some great 12V computer fans in a couple sizes for $1 each! Tons more stuff!
I spent maybe $50-$75 in thrift shops on trip to visit daughter and brought home about $400 worth of stuff!