Tried my own research when i needed large amount of xp books. Might help some new ppl who still dont have their favourite tavern :-)
Both times i used auto janken and in both times it needed +- 175 mil silver for 105 tries
110 tavern 2628 reishi gained
100 tavern 2818 reishi gained
Will be trying 90 and 80 tavern today because I need large amount of reishi for xp books again :D