Is it normal ?

its end of season, unless you are selling top of the line gear it will probably take a while

I notice this is through stash and not through ange. A lot of people purchase purely from insta buy nowadays

How much are you asking for the vase relic?

how do you determine the prices? and do you know what the desirable stats are?

You could always check prices of similar items. Make sure that you do not look up prices with exactly your modifiers but maybe only the valuable ones.

For example, if your items have damage leeched as... or strength/dex/int, or mana regen etc they are usually not woth a lot.

Could you hover one of your items? Press alt to show tiers and make a screen shot. Then we can give you an example why they might not sell.

Sell stuff in the direct marketplace and not through your stash