Hate to say this but unless its real estate and a few other options, you lose at whatever you buy+sell. You dont feel sorry for the people that buy a brand new car and sell it a few years later for thousands less. I am sorry someone has to go through a divorce but from someone who has been there/done that, well thats what happens....as for fish/aquarium things, again other than a few exceptions its done for the love of doing it, not for making money..unless we are all turning into LFS's...
Good luck with your sale and I hope all works out for you in the long run...
Its a battle at times but it does get better...