I think you might have been remembering my post a couple months ago, where I was responding to someone's neopian times article, where they say you should discard all those stupid useless fishing items or pick your own items or tiki tack items, rather than selling them to someone else who also can't use them for anything.
I was agreeing, and went a step farther to say I wonder if we could buy all the ones currently for sale and discard them, stuff like dung, petrified bones, broken fishing poles, broken left sandals, etc... things that you just can't use at all, that are totally useless, and get rid of them. The idea was not to drive the price up, but to kinda clean up the server of all the useless junk. Kind of a role-playing noble anti-litter program, I guess...
I then did an experiment on, I believe, broken left sandals. I wanted to know how much a person could spend on buying them and discarding them before you'd go broke. I don't believe the price of them would ever go up, even if you did buy all the 1, 2, 3, even 5np ones, because they are truly useless. Only a few people are going to want them for a collection or a gallery, so they won't really ever drive the price up.
So, I was partly trying to find out how many of them were up for sale (and see if I could ever get to the end of the list), and partly doing my neopian duty throwing away trash that nobody was ever going to use.
I actually abandoned the experiment out of boredom after an hour and a half, because really, have you ever noticed how freaking boring it is to buy a hundred + of the same thing? and since I never made any progress... I mean, I spent about 150 NP buying them, and still never got to the bottom even the 1np items, meaning that there were more than 150 of that item for sale (big surprise). So it would take a long time before you'd go broke, since they were all really cheap, but there are SO many of them for sale, that I think ANYONE would stop of boredom before they bought enough of them to incur a big cost. Even if you were really patient and made it all the way up to 1000 items...
However, I too remember reading, I believe in the editorial, something about inflating the prices of things by stockpiling, which they said was not allowed. I'd have to find it though.