And another point not to be missed. If you use one of Jon's kits, and apply it carefully and correctly, you will be in a better position to resell your camera if you ever decide to upgrade to a different one.
Worth noting is that Jon has carefully selected the foam for its camera-friendly properties. For example, the foam is a low/no VOC (volatile organic compound) material. This means that as the foam ages it will not begin to outgas and leave a thin residue on the rear side of the camera lens.
For example, late-model Yashica TLRs have a known issue where their internal lubricants can outgas over time, leaving the lens surface with a haze that must be removed. Situations like this can affect resale value, if a prospective buyer knows a servicing may also be required. Jon's foam will not do the same.
The other thing you are paying for with Jon's kits is the precision cut and fit. I recently re-foamed a Mamiya C330S TLR and was darn glad I didn't have to try to precision cut the 1.5-mm strips. I believe I paid US$12 for the kit.
As of 09/22/14 Jon was reachable at:
jon_goodman@yahoo.com
Ken