Brendan Moody wrote:
Budget wasn't involved in using Talisa rather than Jeyne. The producers simply felt it was better if Robb breaking the alliance with the Freys was an entirely free decision based on twue wuv rather than an issue of honor and the result of a deception. If money had been an issue, they wouldn't have ended up featuring the character so prominently and making her a regular this year.
It is a lot cheaper for them not to have to build sets for the Westerling castle, feature the battle for it, etc. and it means that they don't have to give Cat stuff to do while he is gone.
A single actress is cheap. It isn't like they spent any time developing Talisa anyways. One conversation about where she came from doesn't a character make.
Robb has spent most of the last 2 seasons sitting around camp or sitting around Riverrun. If you don't think that was for budgetary reasons I really don't know what to tell you.