This is a 3-pin charlieplexing board, so that makes n^2 - n = 6 LEDs.
This board makes use of the smallest size on OSHPark, which is 0.25x0.25 inches.
That's ¢30, delivered. (Please order more than that, though! OSHPark deserves your support ;) )
It uses 0603 LEDs and Resistors (for red LEDs, I'm using 75 Ohm. Remember to halve the resistance because of charlieplexing --> two resistors in series with LED in between!)
A reel of 100 0603 LEDs can be found on Ebay for $4. The resistors cost me $1 for 100.
Oh, both of those have free shipping.
So, these things have a per-unit cost (without headers) of ¢10 + ¢24 + ¢3 = ¢37.
That's pretty good, right?
Impressive! The size of this charlieplexing board at 0.25x0.25 inches is so compact and perfect for my project. It's great that you made the most of OSHPark's smallest size option see this all size inches, mm, centimeters, you can see here https://calculatepoint.com/8x10-inches-in-cm-easy-conversion/