So I just bought "everything" needed to make these pens: (as far as I know)LEDs = .20 cents (come in packs of 5 at the place I found them)switches = .2 cents (I bought 100 for 2$)Pens = .50 cents (at walmart)battery (not sure, I just use one i have), but I think that aaa would be bestwire = free as well, just grab some network cable and have at itso basically these pens are like $1.50 maybe 2$. Maybe more if you're going to buy a mount for your battery (rather than using tape, like I was thinking So a reasonable mark up would be based on a %, but instead on time. No one is going to sell these things for $2.25, that means they'd have to take like 2 seconds to make. I imagine there are several people that would sell them for say $10On the other hand, buying in bulk is a lot cheaper, and possibly someone might be willing to sell the parts needed for cheap (like if you're looking for small switches let me know .