Highball opens a negotiation with an extreme, implausibly high demand whose purpose is not to be met but to anchor. Anchoring is one of the most robust findings in judgment research (Kahneman & Tversky): an initial number silently reshapes the range a person considers reasonable, and Galinsky and colleagues have shown the party who makes the first offer often captures a durable advantage. Once a sky-high figure is on the table, your counter tends to land higher than it otherwise would, and any eventual “compromise” sits closer to their target than to fair value.
An aggressive opening is not automatically manipulation. Stating an ambitious but honestly held first offer — one you can justify with comparables and are prepared to defend — is legitimate hard bargaining, and skilled negotiators do it openly. The tactic crosses into manipulation when the figure is chosen for its distorting power rather than its defensibility: an anchor with no rationale, deployed to drag your judgment off its footing before you have checked reality.
What makes the highball dangerous is that anchoring biases even people who know the effect exists and who are well informed — awareness dampens it but does not erase it. The reliable defense is procedural: decide your target and walk-away from independent data before you hear their number, treat an extreme opening as a signal to re-anchor rather than to counter, and keep pulling the conversation back to objective criteria.