Just got done looking over my world book.. 1943 proof penny, 104 minted, value...$55 1959 proof shilling, 900 minted, value...$12.00 1943 proof shilling, just 104 minted, value $165
Since sales of these items must be extremely rare, they may be going by last recorded sales which could be 50 years ago, or they just picked a number from out of a hat. Put it this way, can you find any examples of these coins having been sold recently to prove them wrong? In general, any British Commonwealth/ British Empire coin minted before countries started churning out masses of NCLT are in strong demand and sell well, the world population of British Empire collectors is probably as large as the domestic US population of US coin collectors. All the dates you mention are before the informal cut off date of 1960 which marked the end of what I'd call real coin making and the start of coins with no other purpose than to part gullible collectors from their money.
Those prices are way off, the 1943 proof pieces are worth anywhere from $300 to $700+ depending on denomination. A complete 8 piece set is worth between $4,000 and $5,000. Still not as high as you may expect for such low mintage, but collectors for these coins seem to be very discerning of their coins.
Catalog prices are very subjective - could have been the contributor that submitted those prices had old information, or had an ulterior motivation to driving the price one way or another. For a long time until the change in government in SA the coins were a bit overlooked because of the boycotts of that country.
You would be a seller everyone will flock to if you sell such coins at catalog value. Here's one example: http://www.ebay.com/itm/South-Afric...D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
