Budget for a white elephant or secret santa exchange.
Gift exchanges set a cap on the gift price, not on what the evening costs you. Tax and a few units of wrapping push real spending above the cap, which is why the outlay figure here adds both — a flat three for wrapping is a realistic allowance. The headroom line shows whether your chosen gift respects the agreed limit, which matters because caps are what keep the exchange fair.
Exchange outlay
Your outlay = gift price + gift price x tax/100 + 3 for wrapping; headroom = spending cap - gift price; pool value = cap x participants
Conventionally it refers to the shelf price, so tax and wrapping are extra. Budgeting for them avoids the awkwardness of quietly going over the limit.
Slightly under is safe and normal. Coming in far under is what makes an exchange feel unbalanced, since everyone else is buying to the cap.
Something generically desirable at the cap, or something memorably absurd. Highly personal gifts work poorly when the recipient is decided at random.