There is an eastern pass called European East Pass. In my opinion this is a waste of money at the price is five days in a month for $160. This only covers Poland, Czech Repbulic, Slovakia, Hungary, and Austria, the later two which are already covered under a Eurail Pass. Individual countries also have their own rail passes.
When I traveled through Eastern Europe, the most I paid was $40 for a ticket, but that was for a long trip (Warsaw to Prague). Most tickets are very cheap. A lot of tickets seemed to be $2-$3 per hour of travel, so many of my tickets were around $5-$15.