Interesting topic, rebel1. I'll just make some theoretical points (or points of logic), as I view them to be, with two disclaimers: charity is good; and I enjoy HC.
* conflating HC and charity:
Point 1: charity is an individual choice, imo. If I am one of those who prefers to give money to a person on the street with a cardboard sign (and I am), I would prefer to give there, instead of another's anointed/appointed charity;
Point 2: as someone else said, if I give money to HC and they pass on 100% to charity, it does not financially benefit HC, and the only beneficial reason would be for HC to be seen as a good corporate citizen. It could be a pest for HC to collect dough to then pass on- it would be more like having a role as a "Charity Broker", which would take time out from the saite to do an unrelated activity;
* HotCopper members as payees: We do have some kind of "pay" system here, although it is not in the usual pay way: as free members, who are able to vote for HC as the best trading chat site, HC is then able to use this info, to relay to advertisers, to make more revenue. Equally, as HC can say there are more members on HC than any other chat site, they can again use this info for advertisers, as it makes the site more attractive to advertisers. HC then wins.
On what HotCopper is: HotCopper may be seen like the media or free TV: we get it free, and advertisers and the owners benefit. TV and free media (and HC) basically run on advertising, and it's a good model. If one considers all of these media as a "shell" for a shell for advertising, what the owners have done is find something the public wants (entertainment, news, share trading), and then can build it to a point of essentiality, the revenue will come, and everyone benefits. As a user of HC and other media, I benefit greatly, but I am aware this is a paid revenue site- not a charity;
On the affordability of trading costs (as per peaceAKKI's post): trading costs, platform costs, conscription costs (to newsletters, AFR etc), do add up. A stuffed market does not help. The costs of living are high, in my view. An added fee (to charity or not- to members it would still look like a fee), would make some think twice.
