Hi Allan,
Diamond Point has a couple things going for it. It was big enough that pens do turn up and it used some really pretty and sometimes exotic colors. The pens are not high quality. The nibs tend to be small and the trim finish fragile. Had these been done in the same quality as another smaller-make, funky-color company-- Leboeuf-- the DPs would be awe inspiring critters highly sought by collectors of quality pens.
Alas. The big contour and pretty plastic is about all going for the Diamond Points. But, as collectors have branched out from pursuing just the best from the big guys and a few of the small guys, 2nd and 3rd tier pens in some cases have developed a following. We certainly have seen interest grow in generally lower-tier Sheaffer sub-brands for example.
Diamond Points occasionally go nuts. Of course if this pattern repeats enough the situation will no longer be "nuts" and will be then "routine", though serious and longtime collectors might still wonder why low quality pens are pulling Duofold/Leboeuf/Waterman OS prices. So it goes.
Auctions sometimes get hot because two people (perhaps wrongly in the view of the cognoscenti) won't let go. Or, given there are some people who do pursue DP aggressively (which is fine), perhaps this one was a color they had not seen (though there are many funky color DP's and so few pens show up that most funky colors do not come on market very often) prompting "I must expand my collection" thinking.
I do hope the bidders are not mixing this sort with quality OS pens by major makers, Lebouef, and other good pens.
regards
david