Got into this late and many of the good comments have already been said, but I'll throw my two (ten?) cents in anyways
8 Competition Pushbutton 13.60
16 Pushbutton with Horizontal Microswitch 28.80
$42 in pushbuttons, not sure what you are using the Comp's for (or why 8 of them), but regular buttons are on sale for $1 each, so that's a $18 savings there. You could use less expensive buttons for the admin functions, but it's probably not worth it. Recommend using
www.therealbobroberts.com over Happ, as already mentioned.
2 Optical Rotary Joystick 94.40
not much to say here, Druin's
http://members.rogers.com/druins22/ls30/interface is $45 and you used to be able to get SNK's from
www.videoconnect.com for $15.00 each, so you would save $25, but they don't work well for non-rotary games, so I would stay with what you have.
1 High-Ball Trackball w/Harness, Black 95.65
I think someone mentioned Betson refurbished joysticks for like $30. Otherwise WICO 3-inch's are $50. If you don't mind the smaller size, WICO's 2-1/4 TB is $25 and you can use billiard balls in it. Finally, I picked up this 2-inch usb trackball
http://shop2.outpost.com/product/2422410 for $2.99, but it's back-ordered (hasn't arrived yet) and I don't expect it to be arcade quality, but for occasional use and for the price, it can't be beat.
1 3" High Ball Trackball Mounting Kit, Clear Zinc 18.20
Recommend: Atari 3" TB mounting plate, black dimpled $10.00,
www.therealbobroberts.com<edit> 2 SlikStik Tornado Spinner $180
Recommend: 2 OSCAR model 3 spinners - 42.00 each. No offense to slikstik, but you can buy both OSCAR's for LESS than ONE tornado. OSCAR's PRO at $61 is a better option, but you wanted to save money and the Model 3 works well.
1 Ultimarc I-PAC2 39.00
Consider: KeyWiz Standard - $33.00
www.groovygamegear.com, lacks a keyboard pass-thru, but otherwise does almost all that the I-PAC does and RandyT's shipping is cheaper if you're U.S.-based (or probably to Canada also).
1 Ultimarc Opti-PAC 44.00
Recommend 1
www.oscarcontrols.com USB interface kit $9, saves $35. What you lose is the ability to auto-switch to the active control. You can wire everything up to one interface if you aren't worried about bumping your trackball in spinner games, or . . . OSCAR has a circuit here
http://www.oscarcontrols.com/DPDTswitch.shtml for using a DPDT switch to select between a spinner and a trackball. I am sure you could use a 3-position slide switch with two poles to select between your tracball/rotary joys/spinners. OSCAR can prolly tell you how to wire it up (Sorry to put you on the spot, OSCAR)!
2 Oscar Controls 2-way Restrictors 16.00
2 Oscar Controls 4-way Restrictors 20.00
1 Oscar Controls Diagonal Restrictors 7.00
2 Oscar Controls Joystick Mounting Plate 30.00
Recommend: Buy only ONE Joystick mounting plate for $15.00 and use as a drilling template. It looks better and saves you money. Be sure to read the instructions here:
http://www.oscarcontrols.com/customize_hotrod.shtml and mount your joystick using the 1/4-inch hardware and then one at a time swap out the carriage bolts, as the joystick centering is critical.
Except that shipping charges will eat you alive, I would try without the restrictors first, then add the 4-ways and diagonal, then only add the 2-ways if you felt you really needed them.
Hope this helps a little, looks like using a 2-1/4 inch TB and my other suggestions saves you $252 dollars and leaving off the restrictors saves you over $300 !!!