Some quick calculations on AV modding prices

1.76 per jack, 3 jacks for dual mono - and just to be nice I'll pay extra for color coding because that's what the stoneagegamer people did.
yellow - http://www.digikey.com/product-detail/en/RCJ-034/CP-1415-ND/408502
white  - http://www.digikey.com/product-detail/en/RCJ-033/CP-1414-ND/408501
red    - http://www.digikey.com/product-detail/en/RCJ-032/CP-1413-ND/408500
$5.28 on RCA jacks

$0.22 for a fairchild made 2n4401 transistor for amplification - http://www.digikey.com/product-detail/en/2N4401TFR/2N4401D26ZCT-ND/458923
running total $5.50

2 1.3k resistors (10 cents each, $0.20 total) - http://www.digikey.com/product-detail/en/CF14JT1K30/CF14JT1K30CT-ND/1830353
running total $5.70
33 ohm resistor (10 cents each, $0.10 total)  - http://www.digikey.com/product-detail/en/CF14JT33R0/CF14JT33R0CT-ND/1830315
running total $5.80
220 ohm resistor (10 cents each, $0.10 total) - http://www.digikey.com/product-detail/en/CF14JT220R/CF14JT220RCT-ND/1830334
running total $5.90

I have a huge amount of cable, but if I wanted to buy new wire I'd have to buy a longer length of it. Assuming I need about half a foot of wire for each board I make, and I can buy 100 foot intervals for $34.54, I could make 200 boards for that.
This is the wire: http://www.digikey.com/product-detail/en/3051%2F1%20BK005/A3051B-100-ND/281576

(5.90 * 200) + 34.54 = 1214.54

1214.54/200=~$6.08 PER BOARD in components.

Now for the boards:
You can get a 3x2 inch protoboard with copper pads on it for $6.72 (http://www.digikey.com/product-detail/en/8029/V2025-ND/1886431)
There is about 1 inch by 0.5 inches in clearance for a board in the famicom where I've been putting the AV board. that means that you can get 12 boards out of each.

6.72/12 = $0.56 per board.

so 6.08 + 0.56 = $6.64 PER MOD in parts.

I forgot to look at price breaks, but these'd make it even less. And no, I wouldn't be making 200 boards. I already have a shitload of wire that I got free and could harvest and so not spend a penny on wires. Since I wouldn't have to order enough wire to make a shitload of boards, I could order less of everything.

$6.64 total per mod in parts.