How many Points are needed to unlock Preferred Slots and Complete All the Bounty Buffs
All Bounty Talisman buffs follow the same price curve. The game shows the cost of the next upgrade, and that cost increases by +12 Bounty Points every level (e.g. 5 -> 17 -> 29 -> 41 -> 53 ...).
How many levels each buff needs
All buffs require 95 upgrades from base to max:
Total Bounty Points per buff (to max)
Using Total (95) = 6·95² − 95 = 54.055 BP:
Total for all 4 buffs:
4 × 54,055 = 216.220 Bounty Points
+50% Damage: 54.055 Bounty Points
+50% Life Leech: 54.055 Bounty Points
+50% Loot: 54.055 Bounty Points
+100% Double Bestiary Chance: 54.055 Bounty Points
Preferred Slots Costs
There are 4 additional slots of preferred/unwanted creatures that you can unlock.
Slot 1 - Completely Free and Unlocked by Default
Slot 2 - 300 Bounty Points
Slot 3 - 600 Bounty Points
Slot 4 - 900 Bounty Points
Slot 5 - 1.200 Bounty Points
Total to Unlock All Slots: 3.000 Bounty Points
So considering every buff needs roughly 55.055 Bounty Points, the best strategy is to focus on unlocking the slots first, as they are cheaper, and then focusing on doing tasks with 5 creatures with 5x more chance and getting a better task to progress your points focusing on the Bounty Talisman buffs.
Total to Unlock All Slots and All Buffs
You need 219.220 Bounty Points to fully maximize and complete the Bounty Task System. You can of course continue doing tasks for experience and for Highscores after that.
Edit: Since at some point the % amount of upgrades start to decrease to 0.25% and 0.1%, I will update my answer later with the correct values.