Is this supposed to happen?

It doesn't happen super often, but because of the rarities of SubQ items they can be asked for occasionally by some quest givers. Just quit the quest, since there's nothing else you can really do (unless you want to waste the sP).

First time this happens to me, looks really stupid tbh, should be fixed (oh a newbie paying 500k for a subq item assuming it will worth it like every other single quest they did...)