can probably be made for around k plus labor... for a little more you can turn it into a nice bunker... (use bags of cement and stack them around them and wet them down...,, same with the roof and then add rafters and straw bales...
Bags of cement would make it expensive as hell, cinder blocks with filled cores would be as good, better in some ways since they could be readily reinforced. Cement or bales, it'll be dark as a dungeon in there. Windows would be a nice touch, and rat walls almost a requirement to keep critters from taking up residence underneath. Good basic idea.
Speaking of windows, I saw on NatGeo Doomsday Prep'ers last night some really cool Window Glass that was BulletProof when shooting from the Outside/In, but allow firing from the Inside Out.... .... That is cool Technology....
I'm thinking filling the cinder blocks with gravel ( Joel Skousen idea ) for ballistic purposes but will need to view it on my PC as print is so small on the IPAD I can't read it. Lol. Getting old quick
Cinder blocks unfilled $1.69 each 8x8x12... bag of cheap cement 24x36x8 for $2.49.. maybe it's the location... prices are from Lowes... no discount...YMMMV
Here's an interesting idea, for doing the outside of the building. Haven't seen much as far as testing of this product, but if it behaves like they say it will, you could almost put it on like a stucco coating, over the outside of the cinder blocks.
There is also, Grancrete. Sprayed on like Gunite, it offers a lot at reasonable cost. You can read more about the Grancrete family of products including examples of projects we have completed and technical details about our products. Another interesting product is papercrete. Often touted as a DIY product, I place it in with straw bale building - this is to day, get help. Finally, rammed earth is making inroads in the US these days. Rammed Earth Solar Homes Inc. has many interesting photos.
