I first want to say that this project is for a charity auction that happens a couple times a year and we would like to remove all paper from this process since the paper requires 7 people to handle and deal with and is way to frantic!
There are around 100 electronic displays we need to make for our next auction. We want it to be as low cost as possible. Right now we have settled on a 4-digit 7-segment LED display with an ATTiny chip. This gives us 4 digits and since the auction is by whole dollar amounts we won't reach anything above $9999 though above $999 will happen. This just straight cost (no enclosures, solder, boards and such) puts us around $4. Adding a battery case or even a wireless chip drives the cost up a bunch.
So my question is, what tricks can we do to drive the cost of this project down? So far the best we have come up with is to chain multiple displays together and drive it off one wireless chip. Any other tricks anyone can think of?