If you like the bike and it rides well, it's certainly worth the $140 you've got into it. You can get a set of cotters for it on ebay for $9.95, you need 9mm cotters with the 3/4 cut style. Look at the pins, and the taper should go 3/4 of the way up the pin. Most that are sold now are barely 1/2 cut and will bottom out before you can thread the nut on them. It's a cheap fix.
VINTAGE BIKE BICYCLE CYCLE CRANK COTTER PINS BIKE PEDALS 9MM FRENCH COTTER PIN | eBay