I've done the same for my chargers as well (as in using Sugru). I love your idea of making a mold for better finish as well as selling the "robustified" chargers. I think there will be a market for this, but best of all, I think you can pull this off on demand too (in a way?). I also think the $99 charge is fair.

A quick back of the envelope calculation is as follows:

$80 for 85 watt charger on amazon [0] + $3 * 2 for Sugru on both ends of the cable [1] + $5.95 for USPS priority 3 day shipping [2] ~= $92

With this supply chain (if it can be called that), you can still estimate shipping the charger to the end consumer within 6 days (2 days with Prime shipping with Amazon + 3 days for USPS). I did not factor in the Prime membership and the mold in the costs though, but it can be factored in fairly easily. Also, I chose to use USPS shipping costs, naturally your mileage will vary because your company/business probably has higher costs (cool service by the way, and congrats :))

[0] 85 W charger: http://amzn.com/B004L6MLPQ [1] Sugru 8 pack: http://amzn.com/B00EU7DBNM [2] Small flat rate box from USPS: http://pe.usps.com/text/dmm300/Notice123.htm#2517977