I actually stopped looking on Craigslist since a lot of people feel they should get retail.
Tanks/filters and the like are like cars (Not Collector cars)...they depreciate as soon as you buy them and quickly.
A buck a Gallon on a clean tank(no issues) is decent price.
Any filter should be 25% of Retail (Amazon Retail not MSRP)
Stands and Hood (25% to 50% Depending on condition etc) and if someone is "Selling as a Set" they should be giving you an additional Discount IMO
Now I have a Couple of Guys then get used stuff (Flea markets, closing LFS
etc) and I just Reach out to them if I need anything and DIY the rest.
I do use Amazon for about 95% of my new purchase needs.