I ran the numbers at a few points over the years, mainly when "cartridges are too expensive" came up as a topic of discussion.
I have a whole bunch of electronics vendors but never found anybody selling ROM chips of a suitable size (at all actually, let alone at volumes I would want). To that end I usually substituted for NAND. If you want to try aliexpress,
http://uk.rs-online.com/web/ ,
http://uk.futureelectronics.com/en/Pages/index.aspx?OL=GB&Language=en-GB ,
http://www.digikey.co.uk/ ,
http://www.jameco.com/webapp/wcs/st...splay?langId=-1&storeId=10001&catalogId=10001 ,
http://cpc.farnell.com/ ,
http://www.jaycar.co.uk/ ,
http://www.element14.com/community/index.jspa -- all sites that will sell you parts by the reel and are used by big boy electronics makers all day long you can, I struggled though.
All the (mask) ROM chips I found were small things aimed at basic bootloaders and what have you for embedded electronics.
Equally Garmin and such will sell me an SD card with updates on it so it would seem to be a bit viable
https://buy.garmin.com/en-IE/GB/map...rd/c452-c454-atFILTER_FEATURE_CARD_01-p1.html
For discs I would usually use pressing plants as they they have costs available. It does not scale the best and some of those were from the plant in just paper wallets but I assumed at the volumes being dealt with it would probably even out between 1 million pressings of a disc and 3000 for a small run for a company.
http://www.duplicationcentre.co.uk/prices.html
https://www.discmakers.com/quoter/default.aspx
I don't know what cuts Sony, MS and Nintendo take and if that is in addition to anything the blu ray peeps leverage or instead of but it should get you ballpark figures. The difference in ballpark could well be margin destroying but it is not like it is dozens of times more expensive like it might have been at various points in the past.