So it really depends on what you're trying to accomplish. There are a lot of weekly tourneys around that are there for fun, and some are small stakes cash, but usually the buy ins are under $50. Part of that usually goes to the host, and sometimes some of that goes for food, so at $40 a head let's say, you might go $10 to the host, $10 for food, and $20 to the pot (or maybe just $20 to the host if they take care of food, which is great if someone breaks out a BBQ or something like that). At 40 players though, you're looking at an $800 pot, which isn't bad for an afternoon of fun pinball.
If you're not familiar with formats, there are tons of them out there. Some of the main ones:
-Herb Style (aka pump and dump):All players play the same bank of machines. Each entry gets you one chance on a given game. Top score on the game gets 100 points, 2nd is 95, and then I think it goes 90, 85, 84,83,82,81 etc. A "ticket" is usually 5 or 6 games. There might be 10 possible machines in play, so your top 6 placements count. The catch is that you can enter as many times as you want, so people will keep buying new entries to up their rankings. At, say, 5 bucks an entry and 5 entries for $20, you can build a decent pot, but it's also one of the slower moving formats. Lots of waiting around.
-PAPA style: Basically, a Herb tournament, but your scores have to all be on the same attempt (ticket). It's a hard format to run, and hard to explain, but it also rewards consistency.
-Match play: Players are grouped into groups of 2, 3, or 4, play one or more games, get points on how they place within their group, then repeat. 4p match play is a good way to max out wpprs. Again, can be a lot of waiting around and not playing, since in most cases you're waiting for all players to finish a round before re-drawing.
-Single/Double elimination brackets: Usually used for playoffs, but could be the whole tournament. Runs the risk of eliminating someone quickly though.
-Flip Frenzy: Very popular now. It's basically 2p match play, but on a queue, so you're almost always playing.
-Strikes: Match play, but with each "loss" counting as a strike. Could be 2p groups (1 strike for a loss) or multiple players (1 strike for 2nd, 2 for 3rd, 3 for 4th). N strikes and you're out of the running. Again, there's a good chance you're done really fast.
I'm sure there are a bunch of others that I'm forgetting. There are a lot of ways to play pinball.
As for number of games? Depends on the format. A Herb tournament needs a decent sized bank. Probably your ticket size *2, maybe with a game as a backup. The catch here is that your tournament games have to be as bulletproof as possible. Game goes down and players are going to be pissed. Match play you obviously need enough to fit all the concurrent matches, ideally with at least a 30% buffer, both for variety or for when something breaks. More is always better. Again, games need to work, and work consistently.
Now, if you want to have a NIB game as a grand prize? Well, do the math. If you do a Herb style pump and dump, you can sell entries, but you'd need to sell a lot. There was talk about a "high roller" tourney with $100 entries a while back, but the number of players who'd be in for that would be pretty minimal. To do a match play tournament, you'd need something pinburgh-scale, and we've never gotten close in Canada. The CNE tournaments had a ton of players, but nothing close to that as a grand prize. Besides, even if there were something that lucrative in Canada, I know I wouldn't bother entering because it's probably a 75% chance that Adam or Jack will win. There's also a good chance that with a valuable enough tournament, a bunch of the US players will come up and win our money.
