I don't now if this is a glitch or not,
but my peep Is an online poker pro.
I looked at the bank when he was level
7, and it said that he was making 520
a day. I was happy as I could only
imagine what he would make as a master.
Then, the next day he became a master
and now he only makes 240 a day. Is
this a glitch or is it a tongue in cheek
joke referencing how unreliable/unpredictable
gambling is?

Your second guess is right. The are a few other jobs involving gambling and market trading where income can go down as the peep reaches a higher level.