Thank you for playing and for the compliment + feedback! Yes, I must confess that I ran out of time to experiment with any proper balancing, so the highest two tiers of summon are ridiculously more cost effective than the rest of them.
I had a bit of a headache trying to sort the gravestone sfx and in the end decided that the player should only be clicking it for the very beginning of the game (hopefully) so sadly had to half-arse it. But fully agree with your thoughts, I'll try playing around with a more significant pitch shift!