The absolute cheapest way to make DiY Augmented Reality.
It uses the 0.42" OLED SPI display which can be connected to Arduino or anything else that uses the SPI.
It costs less than 4$ (Look for the discounts) to build this thing and that includes the display itself.
Display driver - https://www.patreon.com/posts/124549583
Sample Aliexpress links (You can find chepaer ones ):
Prism - aliexpress.com/item/1005007827057946.html
Small Lens - aliexpress.com/item/1005008549627889.html
Big Lens - aliexpress.com/item/1005008522975790.html