i think it is very silly to buy a bag in the hopes of making a little profit in the future. buy it because you love it and will use it. the "investment" is the number of years you, and probably your heirs, enjoy it.
I've stopped looking at any bag as an investment - I'm trying to only buy what I absolutely LOVE, regardless of anything else.
I only buy bags that I like and know will use ... I do think of them as an investment ~ but not monetary wise. I don't buy and think of how much they will be worth someday or the resale value, because then that takes the fun out of shopping for me!
I say they are my "investment" because I use my hard earned money and I know I'll use them for years to come, and when I'm gone ~ my daughter will. And her daughters later on in the future ... that to me is an investment.