They start at about £50 on ebay - but if those are anything like the £50 ebay electric mandolins there will be much to do before they are playable. I don't know whether violins can be transformed as to playability as readily as guitars and mandolins can (at least intonation is not an issue), but if so you could have a usable pluggable for about £200.

You can finish up in the several thousands of pounds - Bridge fiddles (no relation, based somewhere near Canterbury) are I am told well thought of.