I’d propose raising the prices for direct buy-in, and holding a number of lower fee satellite events that award entry tickets in the run up to the main event.
This means more people can get a shot at entering the main event via the satellites. It means there is a higher prize pool thanks to the higher entry fee for direct buy in, though still allows people to buy in to the larger comp via satellites for a discounted price.
These satellite events could also be international, with tickets pre-paid for and distributed to event organisers around the world (who may wish to further juice the pot by including money for hotels/air fare in the prize money).
This is exactly how the large poker events run, and I’m pretty ecstatic that Pinburgh has proven itself more than popular enough where this seems feasible. I’m also of the opinion that a larger prize pool will attract more attention from media and give Pinburgh even more prestige as THE pinball event of the year, much like the WSOP is the poker event of the year.