Maybe it would be best if you didnt answer if you dont know.
You can hold 100k per charachter, and 1000k in storage. So if you have 4 char in post-searing, you can hold a max of 1.4 million (4x100k + 1000k).
Once you reach that Ecto is cuurently used as a larger denomination of currency. Ecto seems to have a fairly standard going rate of 10k per. So if you run out of cash storage or need to purchase a weapon or upgrade for more than 100k use Ecto
(please no "nothing is worth more than 100k" preaching from you poor folk).