In one sense, I concur with nelson's answer. Gmail accounts are now
available to many people in the United States with mobile phones, and
will cost many of these people nothing or next-to-nothing to
"Create a Google Account - Gmail"
Accordingly, a new Gmail account is worth nothing or next-to-nothing
in a market of users who can establish new Gmail accounts without
difficulty. I am one of the people who can do that. The only value
to me for a new Gmail account would be in claiming an account name
that I like.
However, I think that a Gmail account that I've started to use is
worth more. I would not part with the right to see the messages I've
collected, the addresses I've stored, etc., for free. If I lost my
password and couldn't get it back, I'd feel I had lost something of
significant value. The time and effort that I have spent filling up
the account, and the usefulness and entertainment of the conversations
in the account, are continually growing in value.
So my answer is that while a brand new Gmail account is worth only the
value of the account name to me, a Gmail account that I've used is
worth as much as the value of the material stored in the account,
which I would measure by the time and effort it would take to recreate
that content if I lost it, plus the value of the content I could not