I am flying LHR -> CLT, one-way. The one-way ticket was over $1000. However a return ticket with the outbound the same exact flight as the one-way, was around $800. I bought the return with no intent of taking the return flight.
If you want to test it out head over to ba.com and try comparing returns and one-ways.
Btw I have seen this behavior from other airlines but British Airways is the most recent/relevant example.
