Not sure but I doubt you can buy current stamps below face value unless there's something dodgy going on .   Call AP and set up a prepaid mailing account

You can buy large quantities at a considerable discount from AP-no different to buying multiples of satchels or registered post stickers.

I do know a seller that does this-its his whole business & I used to buy my satchels & stamped envelopes from him when I was selling.

Just curious oztoprank as to how you need 20k of stamps a month unless you have other ids or run a business elsewhere?