Take a peek at https://www.ebay.com/sch/industry4.0-ppd/m.html
Cheap stuff from a new seller! Only 16 feedback ratings but all 100%. Either a scam, mistake, or a new seller moving parts at cost to build up a reputation. All guaranteed through Ebay either way, so if you want to take a risk like I did, stock up! Between prototyping and teaching, I'm burning through parts these days like never before... and thus hoarding more than ever!
74 cents ($1 Canadian) for ultrasonic sensors, 40pc male/male jumpers, FTDI adapters, much more.
"When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."
- Pablo Picasso