I believe nobody will tell you for sure. That is with the record company.
You can only make estimations. But estimations require to count on a certain approaches and factors.
- how many were really pressed? For a CD production one stampler is used to press up to 8000-10000 copies. This number came from a guy who used to work with Polydor Hanover (West Germany) pressing plant.
- how the company treated those promos after the action is over? I.e. do they ask to destroy or to return the discs back. How strict they are on this matter?
- do the initial owner (DJ or journalist) want to part with the disc? This and the previous will determine how many copies are on the market.
- is a particular promo well know and in demand among collectors?
- are there fakes?
"Too Great To Make You Wait" Flashpoint promo CD does not look as a rare one in the USA. I would estimate the amount between 2000 and 5000 copies (a loose approach might even lead you to up to 10000 copies). A few years ago no less than 10 copies were sold on ebay by one seller. It is relatively rare for the other territories. However, it is well known and is in demand. Thus, the prices for this one on ebay are high. But I would not part with more than $25 for that disc.
The same with Desert Island Survivors Kit (ABKCO promo). This one is not that rare in the USA too. I remember a guy on gemm.com (RIP) that claimed no less than 20 copies in stock for as low as $8. And he did not sell those before the site went dead.
Remastered 2002 hybrid SACD is another example of well known and generally overpriced promo. But it was pressed in HUGE quantities for all markets.
Say Ahh! - not that rare.
The Stones on CD - A Radio Sampler (it is the very 1st full length promo CD from 1986 by CBS) - Das Weissbuch claim 1000 copies were pressed. I would estimate more than that, closer to 5000.
Voodoo Lounge 8 tracks - relatively rare. But fakes were made. So, you know...
And on, and on, and on.
Sure, some Japanese (e.g. Voodoo Lounge Tour Souvenir or 3 Greatest) and other regional editions (like French Bridges to Babylon 5 tracks sampler or French Les Annees Stones 8 tracks promo for Hot Rocks) are hard to get. But even for those I would estimate the amount of pressed in the vicinity of 1000. The main question is - how many of those are on the market.
From my experience - some CD promos of The Rolling Stones are easier to get than the first pressing of a particular retail edition of a CD issued in 1983

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And please do not forget tons of fake 'limited custom made promo CD-Rs distributed among the high ranking executives of the record company only'

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