Simple handgonne was very cheap weapon (what do you think metal tube would cost?) used en masse during 100 year war. It was preferred weapon against heavy armored knights, especially during sieges (vs dismounted knights) its range was not that big, about 10-20m, but was relatively accurate at that range - while you couldnt hit the bullseye at that range, you definitly could hit the man sized target.
Arquebuses came in late 14 early 15.century, again en masse used for example by Ottomans (during siege of Constantinople), later were adopted by Spanish, who used arquebuses together with crossbows. Again, cost of arquebuse wasn't too great, it depended on gunsmith, but higher quality pieces costs more (quality = accuracy and reduced possibility it will explode).
And regarding Native - if you look at all those weapons and armors in Native, you cannot say its 13.century - Full plate armor, gothic plates etc, those were only available same time as arquebuses appeared, Zweihanders for example were used by 15-16.century Doppelsoldners...
so based on items available, Native is more similar to early 15.century and therefore gunpowder weapons should be available.