In a town with 1,000 voters and a 12% requirement, you can talk to your neighbors, spend nary a dime, and get the signatures if enough people are cheesed off. In a state with 8 million voters in the last election, you MUST have money for staff, money for printing, money for communications.
Previous efforts to get signatures in any jurisdiction will give you a good idea of how much money and how many staff (volunteer or otherwise) are needed to get the signatures this time. Take an average of prior signature efforts for any subject, because the more fired up people there are, the easier it gets. Less means harder and more expensive.
I suppose I've been involved in about 100 petition campaigns. It boils down to a formula based on targets and district size. The results are a mini-max. Exceed the maximum and your issue will make the ballot. Fall below the minimum, and your issue will surely fail. In between those two, it's a crap shoot.
John / Billybob