XP prizes

[frosty67]

How are the XP prizes calculated for tournaments, for instance,

I have created a
Hive tournament currently has 11 entrants XP156
Kingdom Builder currently has 12 entrants XP300
Martian Dice currently has 13 entrants XP64

Just wondering what the discrepancy is caused by. Is it the game, length of game, complexity, maximum entrants, popularity...or something else

Thanks

Steve