My DII was purchased for $45. My D2 was given to me for free but spent $60 or so to refurbish it myself. So it didn't cost me anything, really. Then there was a cost involved in getting 105mm and 135mm lenses. I had the condenser lenses already.
Difficulty might be to obtain a suitable negative carrier as 6x9 is not a common format. I know I do not have one but do have 6x7 and 6x8 for my enlargers. Depending on your gear, you can cut your own using mat boards and very sharp knife.
So I'd say it won't cost you anything more than getting to any other sizes provided you have a capable Omega enlargers. I have no idea about Beselers.