1936 Proof-65 halves- why are they 3 times the price of the '36 PRF65 quarter?

The "Guide Book" lists the half dollar's price in Proof-65 as about triple that of the quarter in the same grade, even though the quarter had a slightly smaller mintage. Why the difference? Is it because the half dollar design is more popular, or because the half's larger size may have made it more susceptible to damage, or some other reason? Does anyone here have a Proof 1936 half or quarter?

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Comments
Just for fun, I looked up the PCGS PR65 populations for the 1936 dimes (339), quarters (177) and half dollars (372). And, the current Certified Coin Dealer Newsletter price for each is $1580 for the dime, $1330 for the quarter and $4520 for the half dollar. You can see that far more dimes (as well as half dollars) have been certified than quarters, but that the dimes also bid higher. Again, it is a matter of popularity and demand.
One of the best illustrations of a coin that commands a high price, but which is not especially rare, is the 1907 $20 High Relief. PCGS has certified more than 3700 (including resubmissions, of course) in all grades combined. But, even an MS61 bids at over $7000.
The reason is that many people consider it to be among the most beautiful, if not THE most beautiful regular issue United States coin and LOTS of people want to own one. There are many coins which are much scarcer, yet sell for far less, but which are simply not subject to the same level of demand.
On the 1936 Proof Walker- I think about 2,000 have been slabbed by PCGS and NGC. This is more than half the total mintage. Have most of them actually been slabbed, or have there been lots of "crack-outs" distorting the figures?
Coinguy1,
is the CCDN considered wholesale or retail? I think it is sight-unseen.