Every state employs incentives to lure film productions away from Los Angeles. One incentive is 'soft money' where the state provides services or facilities for free or at a discount and exempt productions from fees and taxes.
Some states offer rebate programs where money (calculated as a percentage of production funds spent in the state) is directly rebated to the production company even up to 49%. Many states offer substantial transferrable tax credits (with tax credit brokers ready to sell to their clients). Shooting in these locations provide significant budget savings and provide tax benefits for investors. The SAG website has a list of all states and their incentive programs: http://www.sag.org/state-film-incentives
So why are most movies shot in California?
California has the best access to talent, locations, facilities, equipment, and good weather all year with plenty of sunshine. California does not offer the level of incentives of other states; although in 2009 the California Film and Television Incentive Program was signed offering Production Companies eligibility for a 20% Tax Credit with the requirement that Feature Films must be from a $1 million minimum to a $75 million maximum budget.
The various state incentives do not effect the 'Production Budget' since the production monies have to be spent to earn the rebates; however, the rebates add to the profit revenue.
Production Companies calculate the benefits of filming on location against out-of-state budget increases (per diems, lodging, transportation, etc.) and calculates the access to talent and crew, props, wardrobe and equipment facilities, etc. For example, you could on the set and a crane fails to operate. In Los Angeles another crane could be on the set in an hour, but in another state that crane may have to be imported and cause days of lost shooting time while the actors and crew are being paid. There is also the appropriateness of the settings. Hawaii might offer a great rebate but filming a classic Western in Hawaii would not work too well.