That will be $1600 for software every 3 years, and $105 every month for hosting. No seriously, let me know and I'll send you the bill.  No? Then shut the hell up.
So that works out to about $1800 a year, or 150 a month to keep the site running...  That's actually a pretty big chunk of change.
How many active users do we have?  and I wonder what percentage of those would actually be willing to pay like 10 dollars a year?  Probably less than 15%.
What was the cost for premium membership when that existed?  and how many people opted in for that?  
Sorry for all the questions.  I just "feel" like there's got to be a way to make this site self sustaining that doesn't rely on google advertising.  I know from work experience, though, that what I feel and what reality is don't always line up.  Still doesn't hurt for me to take a look at it, and run some numbers.