In the year 2000 then internet was crashing, and my career hit a rough patch. I found myself an unemployed web developer, and my now wife suggested I start selling online. I hit hundreds of garage and estate sales every weekend, and after months of accumulating stuff to sell I noticed I had a lot of board games. Selling vintage board games became my specialty. As I cleaned up games to sell and neatly repackage the contents I noticed people have always tried to create their own play money for the games. Most attempts were hand drawn and duplicated on the technology of the time.

It became clear to me I needed to create a web site where people could create their own play money bills. I created a basic site, started some SEO campaigns and immediately got inquiries and orders. Much to my surprise the orders were never for what I thought I was creating the site for (people customizing board games). I learned the market for play money bills was:

Marketing
Incentives
Education
Budgeting
Coupons
Promotion
Gag
Gaming
Special Events
Local Currency
Stage Money
Auctions

We became really good at printing large volumes of bills on various papers, then slicing them accurately. We learned people wanted special upgrades for their play money bills :

various specialty papers - plastic, linen, security
lamination - bills sealed in plastic
embossing - physical impression
stickers - for decorations and security
serial numbers - to pick winners of the holder of the bill/serial
scratch/reveal - scratch able area of bill to reveal prizes
corner cuts - rounded edges
scratch games - full blown scratch off games (tic tac toe / Match 3 Numbers, etc)

We soon realized we were creating more than just play money bills. With all the customization, we could now produce:

Scratch and Wins
Coupons
Bills
Trading Cards
Sports Cards
Notepads
Gift Certificates