JPMC wasn't just attempting to buy a large email list. Notably, they were also attempting to buy _future expected email list subscribers_.
In theory, if JPMC buys the entire company and then lets the company keep running, they'd expect the list to keep growing over time at a rate similar to whatever Frank's user growth graphs indicated.
They also, I assume, believed they were acquiring a group of people with expertise in marketing to this segment since, well, if you have a warm list of 4M people, that means you also have the abilities to build such a list, which is valuable as well.
I'm not going to try and estimate what percentage of the price was what, but I'll point out there's more to it than just the raw size of the email list at the time of the deal since JPMC didn't _just_ buy an email list and nothing else.
To quote the relevant bit:
> JPMC reached out via email to a random sample of the list Frank provided – approximately 400,000 purported customers of Frank – with offers to open Chase checking or savings accounts. Of those 400,000, only 103 even clicked through to Frank’s website.
So a clickthrough rate of 0.026%.
Good luck getting anything close to 10% when you're starting with a cold, and possibly partially trash, dataset.