According to post #122, this site costs about $360K annually to run. I have no idea whether this is a “reasonable” number or not. But there are 330,000 members. If everyone donated just $1.10 a YEAR, it would keep FR going indefinitely.
If just 10% donated $1 a month, that too would pay the bills.
If just 1% donated $10 a month, that too would pay the bills.
etc. etc.
If everyone simply pledged $1 a month today, FR’s funding problems would be over.
According to some others, there are about 20,000 active posters on FR. If every one of them donated $20 a YEAR you'd get $400,000.
With the trouble that it is to get money during FReepathons and the number of people who are monthly or dollar a day donors, it's obvious that a few are pulling the weight in donations.