Airlines use their 'one-way' fares for a number of reasons, other than to sell to a dumb punter. It was/is the basis for excess baggage charges and airlines use them in sharing interline revenue. So the classic network airline will always have high one way fares. Some may also offer 'cheap' one-way fares but the prevailing philosophy is that nobody travels one way, other than ship's crews, students and immigrants - and they have special fares for those.
LCCs like squeezy and cryanair don't do it this way, in fact they don't have round-trip fares.