After reading this answer on gamedev.stackexchange, and this answer here on math.stackexchange, I totally understand how to calculate the payout for a slot machine.
To summarize: In order to pay-out 95% of every dollar spent on a three wheel slot machine, (each wheel has 10 unique symbols) a jackpot match of 10-10-10 would pay out $950.
Where everything breaks down for me is the following.
Say you have a slot machine just like above, with three wheels. However, for every dollar spent (up to five dollars), you light up a new "row" that can provide new sets of "matches" per spin.
Imagine a 3x3 grid, made up of 3 wheels, like so:
Diagonal \ __ __ __ / |__||__||__| - top row |__||__||__| - middle row |__||__||__| - bottom row / \ Diagonal
So for each spin:
- Paying one dollar you could only match three across the middle.
- Two dollars could match the middle row and the bottom row.
- Three dollars could match the top, middle and bottom rows.
- Four dollars could match the same as three dollars, plus a diagonal line from the top left symbol to the bottom right symbol.
- Five could match the same as four, plus a diagonal line from the bottom left symbol to the top right symbol.
How does this affect the probability / odds, and more importantly, how should it affect the payout to keep the machine paying 95 cents per dollar spent?