The Wikipedia banner is great for being the right argument but it is too long. Those that get to the end mostly donate I'd say. Most people think there are a hundred expert staff and the plea and explanation can't be working if that's true. Very few donate.
What about on the Tor front page a donate ?$2 button near concise points.
'Volunteers run Tor's servers at their expense. Press to pay developers to keep tyrants/censors out.'
...apologies if this is the wrong place or process
Robert