Harvesting diodes

I'm new to a lot of this. Still learning. I see a lot of reference to "harvesting" diodes from equipment. Projectors, etc.
Can't you buy them from the manufactuers?

Only in extremely large quantities. It's not feesable for manufacturers to sell small quantities to hobbiests.

Also there's the safety issue... The manufacturers do not like us making handheld lasers because they are dangerous. This could possibly result in legal issues for them if they were to sell the diodes to us for the sole purpose of making handheld lasers.

Edit: Actually, you can buy the diodes in small quantities in samples, but expect a 5k+ per diode.

This page will give you an idea of what buying individual diodes from a distributor costs.
Thorlabs.com - Visible Laser Diodes: Center Wavelengths from 404 nm to 785 nm