Doesn't each 1000 coins added to a progressive equal .5% in payback?
Yes and no.
This is a rule of thumb that works reasonably well, when the jackpot
is near 8,000 coins. So, in that sense the answer to your question is
yes.
Now let me explain where the rule comes from and why it really is not
so good for larger RF payouts. The rule was created on a simplifying
assumption that the RF cycle is exactly 40,000 hands. On a dollar game,
this simply means that when you put in $200,000, your expected number of
RF's is 1. The extra 1000 coins is 0.5% of that investment.
Of course, no machine has a cycle of exactly 40,000 hands. The cycle
decreases as the RF grows. Most games have cycles that are closer to
32,000 hands (yet another approximation <g>) when the RF gets above
10,000 coins. This varies a bit from game to game. However, DB, JOB,
Bonus Poker, and DW all have many changes that cause a sharp decrease
in the RF cycle.
The same kind of thinking gives a better general rule for this. Now
we assume a cycle of 32,000 hands. This is $16,000 coin in. Now we
see that adding 800 coins to the jackpot will produce the jump of
0.5%.
On a quarter game, this means $200 adds 0.5%, but ONLY when the RF
is above 10,000 coins. This is not perfect, but it is all you need
for analyzing a play while you are scouting.
Personally, I have always used the approximation you give, but I think
I will add this refinement to my way of thinking.
QZ