I purchased two gallons of expired latex very late Monday night and they just arrived in Dallas Texas. Just over $50 total (product and shipping)
I can't really attest to the quality as I haven't ever used latex before.
However, I'll share what little I've learned so far:
1) The Latex from Michaels costs $10/16oz. For $15 more you can have a gallon of expired latex delivered. +150% spent gets you 800% more product.
2) I've read that one guy used about a gallon to corpsify 4 bluckies. Using the stuff from Michaels will require that you buy two containers ($20) to do just one blucky ($20), or $80 to do the same 4 bluckies.
3) If you plan on making molds of skulls (for either paper mache copies or plaster), you'll likely use the entire container for one mold. One gallon of latex would get you 8.
Of course, if your plan is to only create one mold or to only corpsify the upper torso of a blucky/bucky, then $10 ($5 with the coupon) is all you need. Be silly to spend the extra $15 if i will just end up drying in your garage.