> How much does the current server cost per month?
$7.95 / mo hosting + $1.67 / mo domain fees
> How much would a server cost that can meet our current demand?
That's a trickier question; the current server can meet demand when there are no other users hogging things up. The problem with shared hosting isn't so much the speed (the server we're on is very, very fast for the price), it's the inconsistency, because when other users on the same systems as us start hammering the system under their account it has a knock-on effect for us.
This is why performance can change a lot even with no significant change in users or code.
For a dedicated server that could host us I think it came out at somewhere around $90 / mo, for a VPS ("virtual" dedicated server hosted by Dreamhost, with resources that can't be interrupted) you pay for as much resources as you need, priced at $0.50/10MB (you need to pay for both a web server VPS and a MySQL VPS though)
I would say 500MB for web, 500 for MySQL, would be around $50 / mo (and probably not great performance on average)
Re: money generation. Plura netted ~$50 / mo during the good periods, but many people didn't like it and it was inconsistent. Donations are great but there's no way people are going to donate enough, consistently, to keep us on dedicated hosting.
Ads could probably raise enough for a dedicated server, but although I could go either way it's not ideal.
I think ads with an ability for donors to block them out might be good, but given that the majority of our users are Firefox users I wonder how much of it would be Adblocked out.
re: The donation link being hidden away; where would you suggest I put it? Bear in mind we don't really need donations on this site, and I don't really need donations personally (although I do appreciate them and put them towards the cost of hosting), so putting a donate icon on every page wouldn't be great.
(If we went with Dreamhost VPS we could use their donate-to-hosting-fees button, which I wouldn't feel so bad about making more visible)
These things happen on shared hosting every now and then (and they are a major reason we have so many scripts to try and account for downtime / extended 500 error periods).
Usually what we do is complain and they find the user who's hogging the resources, or move us to a different server, but this is a real hassle, it takes ages, and you have to convince front-line support that it's not webDiplomacy that's doing it every single time. (They just see "memory limit reached" errors, and think the reason is webDip scripts use too much memory, rather than understanding that webDip scripts take so long that they all add up and the combined total reaches the limit)
It would be good to find an alternative, but I'm not sure how to fund it, and having been to many shared hosting places I don't think we'll find better shared hosting