That last one does sting just hearing about it. My specialty has been to find and discover truly undervalued, cool books, buy them, have them for a year or two, discover other cool and undervalued books, sell the first group for less than I paid as nobody else has caught on yet so I can pay for new comics. Usually 6-12 months later, my cast offs get hot and multiply in value. It's a pattern I can't seem to break. Even when I manage to keep a comic for 8-10 years, it still goes up right after I sell.
The only upside is that I mostly only sell to friends and board members so at least they benefit.