The way I look at it as a seller, is I try to price them at ebay low pricing. Sometimes you can't do that for lack of info, so I take a guess at it, or I will just list it at what I paid for it, hoping to break even, which sometimes may end up being higher than actual current values, if it has been a while since you actually bought it.
If stuff doesn't sell, then either there is no interest in that stuff, or it's too high. It's up to the seller to adjust, or in my case I will just keep it, rather than lose a whole bunch on it.
One of the biggest issues for me is a seller from the US who is higher than ebay pricing, plus then the shipping is $8 on a card. I understand what it costs to ship to Canada, but that doesn't mean I'm okay with it. I saw a Dylan Larkin YG for sale on a board yesterday for $30 US, plus $8US shipping. Not that exciting at that price. I can remember not so long ago when the tables were turned, and I use to feel bad for US buyers having to pay way more shipping than we did here. I use to drop my prices a couple, or few bucks to offset things for them, but I've rarely seen that now from any US sellers. I just avoid sales from them now, unless I can buy multiple items to make it worthwhile. I just can't justify paying $18US to add a $10 auto to my collection.
As for lack of highend deals you mentioned in your first post, I don't know why? If I had to speculate, going by my own personal situation, I would have to say there are not a lot of people that can actually afford to buy cards from a $500 pack of cards. I know I can't right now, so I just don't bother with it. That is another reason (of many), that I stopped going to The Expo twice a year. I was sick of almost every dealer trying to sell their highend Cup cards, and didn't have a lot of the stuff I collect in their showcase. Just brand new, shiny high end stuff. It doesn't help matters that most of them want top dollar for their stuff when we can buy it for 20-30% online, for example.
I'm almost always looking to add to my collection, but not at a price that I have to contribute paying for a rippers addiction, or for their table at the show. It also doesn't help that I have hardly no interest at all in the players of today. Sure I collect a few guys, but my money goes to HOF players, who have actually accomplished something in the NHL. Sure Domi, Mcdavid, Eichel, Larkin etc may be very good young players, but to pay top dollar for them now, when they have done zero in the league doesn't appeal to me at all. To each their own, as we say.