I'm going for an Old West feel; my players wanted something like Shadowrun but Western instead of Cyberpunk (I love my players so much). Think Trigun with halflings and dragons. They like Pathfinder, and the Talenta Plains in Eberron seemed appropriate, so I thought, "Hey, guns, cool":
But the Guns Everywhere rule bothers me, because guns are too expensive to be "commonplace" or "widespread."
Guns Everywhere: Guns are commonplace. Early firearms are seen as antiques, and advanced firearms are widespread. Firearms are simple weapons, and early firearms, advanced guns, and their ammunition are bought or crafted for 10% of the cost listed in this chapter. The gunslinger loses the gunsmith class feature and instead gains the gun training class feature at 1st level.
Even at 90% off, 500 gp for a rifle, other things being equal, is way too much. It makes little sense to arm common law enforcement nor soldiery with a weapon like that, nevermind an outlaw gang or a frontiersman wanting a hunting weapon.
So I'm thinking about "Guns Everywhere, No Really," which is my house rule that's identical to Guns Everywhere except that firearms (non-alchemical ammo) are 2% of the listed price. That puts guns in the affordable range (only a little more, give or take, than a crossbow).
The question is, how dangerous is it to do this? Will I break the game in some way I can't forsee? Making touch attacks this common seems to be risky.
Update: Several people said very useful things. Thank you! I've upvoted where appropriate. Here's a compilation which taken together seems to tell me what I need to know. A better way to word my question is probably, "What will change when guns really are everywhere?"
somori had the biggest realization of all:
It will have an effect, because people won't bother with armor. There's no reason to get weighed down/slowed/possibly drowned if people can easily and cheaply shoot at your touch AC instead.
Shannon John Clark was the most thorough about firearm tactics (reworded for clarity):
If you want your players to have fun do make sure that you give them encounters on a grand scale -- guns in a close quarters dungeon get ugly (and fairly simple) fast, though closing and taking/triggering AoO's becomes important. Encounters that involve complex geography and range will make spells & guns more fun and complex to play. Also make sure you understand and are consistent in enforcing cover and concealment and lighting rules (this holds true whatever type of guns you use and equally if you have other ranged characters).
Gates VP said interesting things about tactics, equipment, and magic items:
If you want to includes "advanced" weapons, be ready to really expand your battlefields. melee attackers will start carrying tower shields for cover. Wizards will be watching the ranges on their spells (fireball > rifle). Magic weapons will have smaller bonuses as "Lucky" will be the defacto first buff (after +1).