A Few Newbie Grading Q's

The Sheldon Scale of grading has two important criteria:
1) Amount of wear on circulated coins
2) Amount of bag marks or other other contact marks on uncirculated coins

In neither case is eye appeal taken into consideration. Cameos fall into the eye appeal category
and are prized by some collectors.

The mintage of proof coins often exceeds the mintage of regular issue coins.
Thus the occasional price difference.

I'll leave the technical mintage process to others.

Welcome aboard!

I'm reasonably sure that Proofs are struck on special presses, given that Business Strikes are done at a rate of something like 150 per minute per press. That's the only way you can produce 300 million of a given issue....

Proofs, of course, require far more careful minting, but with sufficient automation in the handling process I can't see any reason why you couldn't create one in less than 10 seconds. That being the case, a run of (per your sample) 40,000 is only a few day's work for one press, and it's reasonable to assume (as you did) that more than one press is available for service. If nothing else, because there are a number of different Proof issues being struck at the same time.

A Business Strike die is capable of a six-digit production run. The same cannot be expected of a Proof die pair, but it isn't unreasonable to expect a few thousand coins from a single die pair. As the microsurface of the die wears away, it ceases being able to strike Deep Cameo coins, into the Cameo category and finally unable to strike with any cameo at all. This, however, can be restored through a polishing process. The Mint is very, very good at it, evidenced by the preponderance of Deep Cameo strikes in the entire runs of Modern Proof strikings.

Even if worn to the point of being able to impart no cameo, though, a given die is still capable of striking a 70 because that grade isn't a function of the surface finish but the detail and accuracy of the strike.

The reason why MS70's are more expensive than PF70's is simple: the Business Strike production system does not lend itself to producing 70's. Remember, we're talking about 150 per minute, and that requires rapid handling after the strike as well as during. Very few coins survive that process unscathed. In fact, there are many Modern issues which get quite pricey at the MS67 level, much less 70.

I don't have too much more to add on to SsuperDdave's post. Proofs, especially the kind with mirror like fields(majority of modern proofs), will be judged for cameo and Dcam. There are exceptions, like matte proofs, which are not judged for cameo or Dcam since the entire surface has a frosted appearance. Cameo is judged independently of the numerical grade and can still grade PR-70 provided it meets the criteria for the grade.

After doing a little bit of researching, I've found on the U.S mint site that as of 2006, they were making an average of 6000 coins per pair for uncirculated American eagle and buffalo bullion coins, 1500 for the proof buffalo, and 300-500 for proof American eagles. A more recent 6/24/13 Coin World article states the die life is averaging 1800 for the enhanced silver eagles, 2000 for the reverse proof silver eagles, and nearly 2300 for the regular proof silver eagles.

Taunom: Welcome to the CCF!

SsuperDdave is correct. I have seen dedicated slow speed presses for proof coins used at both the Perth Mint and the Royal Australian Mint in Canberra.
Each press is continuously attended by an operator, and each coin is examined quickly by the operator, immediately after it is ejected by the press.

Modern NCLT proof coins are contrived. The incused surfaces of the dies are laser etched, and the fields of the die are diamond polished. The planchet surfaces are also polished before striking.

For me, the grading of an 'as struck' NCLT proof coin under these manufacturing standards is pretty much of a nonsense, despite the fact that the quality of the strike can vary, depending on how much quality control the mint is prepared to invest in a particular product.

What should be judged under these circumstances is not the condition of the coin, but the quality of the strike. I have seen some poor quality proof coins, notably from the Valcambio Mint (Italy).
I don't think the Sheldon grading system is appropriate to judge quality of strike only.