There's only one way to personally value if you should pay money on the upcoming cash banner or not, and that's to know what your odds are of getting a unit you want vs. the odds of that not happening.

So, here is a form you can fill out to determine those odds: https://docs.google.com/spreadsheets/d/1VyQWZtvacGZYrL32LUgtUSUE2jbXzxI0RRoqL2tnRE0/edit?usp=sharing

Go to File and choose Make a copy... to save a copy of the spreadsheet to your Google account, and then fill out how excited or disappointed you would be to get each possible unit.

NOTE: This form assumes that Chow will be in the summon pool, but Yun will not. Turns out Chow is not in the summon pool. I've updated the spreadsheet accordingly.

Once you've filled out your opinion of each unit (took me less than 2 minutes, although I had to look up who the heck Jiraiya was), you can make an informed decision as to what price point you would consider buying a random 5* unit.

May the odds be ever in your favor!