Though purchasing an item like this just before the bonus weekend was an inexperienced move, it would be stupid to listen to the people telling you to dump. They clearly have no idea what they're talking about. I'm actually going to head over to suggestions and complain about this sort of stuff, it's getting out of hand.
Don't do what every other noob merchanter is doing and panic dump now. The prices will rise back up to at least close to what they were. As another member mentioned, if there is another bot eradication, they prices will rise again.
In the future, I would suggest not buying potions that people don't use everyday. Especially now that Vecna skulls have arrived, magic potions are only used by mage pkers, which in the scheme of things, are few and far between. Range pots were overpriced to start with, and were also a bad choice. Try prayer, super restore, prayer renewal, saradomin brews, or super sets (with the exception of defence) next time.