Thanks Mike and Dario, you guys said exactly what I had ineloquently tried to say.
I have no official afiliation with any of the resellers here, and I have no problem with group buys on stuff that others sell. For example, CSUSA is a great participant here both formally and informally thanks to Nils. They sell CA, and yet I've gotten in on the CA group buys in the past and see no reason why there is a conflict. But I do like to support those who participate here, especially those who donate to or help support IAP.
It should be noted (for clarity) that although the standard size sold by the resellers is slightly smaller than that used in the calculations above, you're getting the extra grit.
When it comes to deciding whether or not to initate a group buy, it comes down to how much the organizer is going to save. I did a group buy on pen kits, and I saved about $40 or $50. I think I spent about four to six hours organizing everything, printing mailing labels, etc. That works out to a savings of somewhere around $10/hr for me, and if you look at how much we saved as a group divided by my time, we did pretty well. To me, especially from the point of view of the person coordinating the group buy, saving even $1 off the cost of an order of MicroMesh (one 6x3" sheet will last you a LONG time if you're careful) doesn't make the group buy worth the effort. I think group buys are better for commodity-type items like pen kits, or on things where there is a significant price break, like the DVR lathe group buy (which I REALLY wish I could afford to get in on!!!) when multiple items are ordered. However, this is just my opinion; if you think it's worth several hours of your time to save $1 or even $5, then by all means go for it!