I am not Cap1, but since I am in the middle of my keezer build I can give you a rough idea of the costs. Assuming you are starting from scratch but have general tools and a way to cut some wood (I am borrowing the use of my GFs brothers miter saw and table saw)..
Freezer: $100-300 (depending on if you buy used or new and even more if you want a huge one)
Lumber: Collar method - $10.. Fully encased freezer with coffin ~$150-500 (this really is dependent on what you want, I am using oak for my build so it is closer to the upper end of that)
Foam: Collar method - $15 (full 4x8 sheet of 3/4".. plenty left over) Coffin method - $50 (sheet of 2" and sheet of 3/4")
Tile: $75-150 (again dependent on what you want and if you have any kind of tools to do this with.. does not account for a tile saw.. Lowes will do that for you though)
Stain: $60 (this is stain, polyurethane, good brush or two, etc)
Misc: I would account for at least $100 worth of little stuff you just dont think about.. screws, hole saws, liquid nails, etc.
This does not include the cost of kegging equipment.. but if you have even thought about doing a keezer I am going to assume you already have that stuff or know the cost of it. You will need to account for buying extra beer line.. I am going to be using 12-15' per line. And if you do stainless perlick taps those run $30-40 each.
Hopefully that will help.. for the most part the cost can be mitigated through proper planning. I have pages and pages of sketches, measurements and ideas (btw.. if you have not done woodworking before make sure you look up ACTUAL size of lumber when doing planning).