I tend to buy my games on Steam (but made an exception for this game), and put them into four categories:
1) 'I will only play this game if you pay ME for it',
2) 'maybe, if it's on 80% discount sale',
3) 'will buy for max 19.99 euros',
4) 'will buy for max 29.99 euros'
At it's current state I would have paid 19.99 on Steam and considered that a fair price for what I got.
With more endgame goals, and more 'reward for (some) grind' (I'd like to see character skill and proficiency levelling / class development for example. Item quality would be nice too), I'd go up to 29.99.