This is the CMP marked boxes in .30 cal ammo can as well as the Spam cans.
Both hold 240 rounds.
Are they going for the same price or the Spam cans going for a bit more?

On a similar yet different note, where is a good place to research current C&R prices as its been a while since I involved in this aspect of firearms.

Are the spam cans clipped?  Maybe add a buck each for the clips and cardboard sleeves.  Same for the bandos.  Each bando and the sleeves add a little bit of value. 

Going rate seems to be anywhere from .55-.65 a round, assuming its not corroded.  Depends on your area. People might pay at the higher end of the spectrum for the sealed spam can because its all the same lot. 

As far as the C&Rs, cruise pretty much any major gun forum classifieds, gunbroker or gunauction.com to gauge demand, and draw some conclusions.  Its hard to give a hard and fast answer on that.  It'll take some research, or a bunch of annoying "whats my stuff worth" threads various places.