The thing is, to successfully anchor rather than blowing up the negotiation you need to have a solid idea of what the "right price" should be.

Say you're selling an item you know is worth $100. Asking for $125 - $150 sets you up for winning. Asking for $1000 sets you up for crickets.

If you're selling the same item but have no idea what it's worth, you run the risk of asking for $50 because you don't know it's worth double, and losing half the value. You also run the risk of asking for $1000 and having the exercise be a waste of time (and possibly money if you pay to advertise).

If you're buying, again, if you have no idea what the item is really worth, you'll likely overpay without even knowing it.

The bottom line is that to win negotiations you need to know what's a fair price. That knowledge positions you to make a plausible anchor that benefits you.