The West End will be a touch cheaper than Edinburgh, but not much. Typically only around £10 a week at the most. Rents are coming down across the board, so I'm not sure how that will affect things. Trains from Queen Street are relatively frequent, and I know of at least three people from my school who commuted there, although we are going back a few years now. For two-three days a week its easily doable, not sure I'd want to do it all the time though.