After buying the Project Arcade book I went out shopping and found out how much on avg it would cost for items. Let's just say that the parts are NOT cheap and if you don't have a monitor/TV and computer you are looking at some $$$ if you want A-Grade parts.
here is my spreadsheet (hopefully it will take!) of what I found and where:
Supplies            
Name   Quantity   Cost   Total   Link
Clear coat poly acrylic paint   1   30   30   Home depot/Lowes
Gallon of Black paint   2   15   30   Home depot/Lowes
Galon of Primer   1   15.97   15.97   Home depot/Lowes
3/4" inch MDF   3   18.85   56.55   Home depot/Lowes
5/8" 18"x 35" hardwood for CP top   1   15   15   

?
Screws (various sizes)   1   9.99   9.99   Home depot/Lowes
2 1/2" L-Bracket   6   2.82   16.92   http://www.lowes.com/lkn?action=productDetail&productId=45685-53911-ZAB205
2" L-Bracket   4   2.82   11.28   http://www.lowes.com/lkn?action=productDetail&productId=45685-53911-ZAB205
Shelf Brackets (9")   4   3   12   
Cabinet Hinges   2   6   12   
Surface bolt for Cabinet hinge   1   5   5   
Velcro roll   1   2   2   
Grommet Sleves 2 "   1   1   1   Hardware store
Glue sticks   1      2.99   
Wod Putty   1      5.99   
Sand paper    1   5   5   Home depot/Lowes
Caster (3")   1   15   15   set 
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=26222&item=3813810127&rd=1Wood glue   1   2.99   2.99   Home depot/Lowes
Plexiglass sheet   1   $15    15   various sites
T-Molding (black)   60   $0    16.2   http://www.t-molding.com/cart/customer/product.php?productid=3&cat=16&page=1            
Subtotal         280.88                           
Control Panel            
Name   Quantity   Cost   Total   Link
3" Trackball   1   96.4   96.4   http://www.happcontrols.com/wp/item_search.html?item-no=56-0100-10
3" Trackball mounting plate   1   11   11   http://www.happcontrols.com/wp/item_search.html?item-no=55-1101-00
Horizontal Microswitch   25   1.85   46.25   http://www.happcontrols.com/wp/item_search.html?item-no=58-9100-L
1 Player Microswitch   1   1.95   1.95   http://www.happcontrols.com/wp/item_search.html?item-no=58-9111-L1PLY
2 Player Microswitch   1   1.95   1.95   http://www.happcontrols.com/wp/item_search.html?item-no=58-9111-L2PLY
Pushbutton Wrench   1   2.4   2.4   http://www.happcontrols.com/wp/item_search.html?item-no=53-8002-00
J-Stik Bal Top   2   14   28   http://www.ultimarc.com/controls.html
4-way Joystick   1   13.95   13.95   http://www.happcontrols.com/wp/item_search.html?item-no=50-7604-10
SlikStik Tornado Spinner   1   89.95   89.95   http://www.slikstik.com/SearchResult.aspx?CategoryID=4
18 AWG wire 45' spool1   1   5.49   5.49   http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=278-1223
22 AWG wire 45' spool   1   5.49   5.49   http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=278-1221
Quick disconnects-Blade   3   1.65   4.95   http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=64-3132
Spade Terminal (16 pack)   2   1.69   3.38   http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=64-3124
I-PAC4 PS/2   1   65   65   http://www.ultimarc.com/ipac1.html
Optic-PAC USB   1   44   44   http://www.ultimarc.com/optipac1.html
Opti-PAC Spare Cables   1   9   9   http://www.ultimarc.com/optipac1.html
Subtotal         429.16               
Misc            
Name   Quantity   Cost   Total   Link
MAME Roms   1   30   30   http://www.freemameroms.com/
24" TV w/S-Video   1   144.49   144.49   http://www.bestbuy.com/site/olspage.jsp?id=1051806303676&skuId=5336237&productCategoryId=cat03003&type=product
Athlon 2600+ computer   1   413   413   http://www.tcwo.com/cgi-bin/webc.cgi/st_prod.html?p_prodid=1504&sid=44oBmP0-IMSp7Rn
Radeon 9600Pro w/S-Video   1   135   135   http://www.tcwo.com/cgi-bin/webc.cgi/st_prod.html?p_prodid=740308&sid=44oBmP0-IMSp7Rn
Subtotal         722.49   
GRAND TOTAL         1432.53   
This is not including the tools it would take to build the thing, that alone is another $600 at least for a table saw, jig saw, and other equipment. Best to rely on your friends for that!