Update 9mm.json

9x19mm +P+ is about double the price of 9x19mm +P as per my cursory research.

data/json/items/ammo/9mm.json

@@ -37,7 +37,7 @@
     "name": { "str_sp": "9x19mm +P" },
     "description": "Overpressure 9x19mm ammunition.  The round's increased velocity results in superior accuracy and stopping power at the cost of higher recoil.",
     "price": 300,
-    "price_postapoc": 800,
+    "price_postapoc": 400,
     "flags": [ "IRREPLACEABLE_CONSUMABLE" ],
     "count": 25,
     "relative": { "damage": { "damage_type": "bullet", "amount": 2, "armor_penetration": 2 }, "dispersion": -15 },
@@ -50,7 +50,7 @@
     "name": { "str_sp": "9x19mm +P+" },
     "description": "A step beyond the high-pressure 9x19mm +P round, the +P+ has even higher internal pressure offering superior damage, accuracy, and penetration.",
     "price": 350,
-    "price_postapoc": 400,
+    "price_postapoc": 800,
     "flags": [ "IRREPLACEABLE_CONSUMABLE" ],
     "count": 10,
     "relative": { "damage": { "damage_type": "bullet", "amount": 4, "armor_penetration": 4 }, "dispersion": -30 },