How to determine points costs of Tau unit enhancements?
There still is a table for the Ranged Weapons and Support Systems on Page 74 of the 2015 edition of the book. The did clean up the locations of special rules/equipment in newer editions, but if you're used to the older editions this can be hard to find.

Generally Ranged weapons are 14 points and other support systems range from 5-25 points each. One nice thing about weapons all having the same points is you cna swap crisis suit builds very easily. None are free unless the rules explicitly state so, for exmaple: "X comes equipped with with a Burst-Cannon which you may upgrade to a Smart-Linked Missile system for 25 points" or something similar.