In all honesty, if you could only get a refund within 5 minutes of the lock being placed, it would remove the "Oh crap I didn't mean that. Fook!" part of an otherwise functioning money sink.
I once locked about... Idek, 30 chests or so? All in an area that was wrong. None were usable and I straight up lost like 300 regals for it. While that isn't a lot, it's still something.
Perhaps I'm stupid (Lol, "perhaps"), but I don't think I should be punished for simple mistakes that a lot of people seem to also make.
Once the five minutes is up, you shouldn't get your money back. 'Cause like, if you don't notice it's wrong / you've made a mistake in five minutes then... Idek how that's possible.