dammit this is hard, I was told there would be no math. Umm, if I had to come up with something...
1. While your customer service response in emails is top notch, I think you could be more efficient if you had some sort of website form with a dropdown menu of the issue (so it gets emailed directly to the correct person). I'm assuming if I contact Charlie about some issue that is better handled by Luke, he has to spend the time to forward the email.
2. Spare parts - While I'm pretty sure Spooky would sell you almost any part you need, JJP has a smattering of parts on their website. Even if I didn't NEED something I might consider buying a part if I could see pricing (for instance if I liked a certain ramp that I wanted to use in a homebrew project), or I just want a dominos backglass.