Update on availability:
PiZero and PiZeroW can now be bought in bulk directly from RPF(T). PM me for details, and I will put you in touch with the person who deals with bulk orders.
Please note however, that cost per unit when bulk buying is HIGHER than the single unit cost. This is due to the single unit price having very low margins, so that it can be bought by more educational users with limited funding - this is in effect a individual educational discount - which is obviously not available to bulk purchasers. Bulk purchases will need to be in the hundreds to be viable.
The one unit per person limit For PiZero and PiZeroW will stay in place for the foreseeable future.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Please direct all questions to the forum, I do not do support via PM.