Check if the weapon is meta, goto warframe market, price mine 1 plat cheaper than the cheapest if it has garbage rolls.
If good rolls are present i will price it mid range and drop it 50 plat weekly till it sells.
To me plat in hand is worth more than some potential higher price down the line.
Give it time, when the 3rd party API shuts down on 6/30 and mods can no longer moderate as needed, you might see some returners