LEGO User Group bulk purchase.
LUGbulk is a (currently) annual benefit that The LEGO Group gives to all qualifying LUGs. Once a year (usually around December) TLG lets LUGs know that "LUGbulk is on!", and each LUG goes through whatever process they create to work up a list of elements they desire in otherwise difficult-to-obtain quantities for relatively low cost. One important caveat of the LUGbulk program is participants do NOT disclose actual part pricing to non-participants. lest the program be suspended.