
I can't help with where to buy perforated paper from, but I imagine that you might be able to get tickets printed at a lower cost than buying the paper & printing them yourself, especially if you're using an inkjet printer.
I've used Jamjar print in the past for getting event tickets printed, and they're pretty reasonable, as are Leafletfrog who I've used recently for some leaflet printing and was very impressed by the turnaround time - I ordered online on a Sunday night, and had 5,000 leaflets by 9am Weds morning!