Hey man. Ofc get a few opinions if you can. Here's my take:
lvl 5 plate - 10-15 fg
lvl 10 plate - 15-20 fg
A lot of ppl will use max life gear to lvl 10 or 15. Also plates are the least useful type of armor (in terms of which chars can use them).
I'd try throwing them up on MP for 15 fg and 19.99 fg (respectively) and see if you get any bites. If they don't sell, no loss, and you can drop the price and put them up again.