What each perp costs to trade, against how much it trades: the expensive ones sit above the rest.
Spread against 24h volume for 200 assets. Lowest: BTC, 0.013.
One dot per asset, both axes logarithmic: lower costs less to trade.
Further right trades more over 24 hours. Lower costs less to trade on the measure you pick: the bid-ask spread, the slippage takers paid past the best price, or the bar range.
Both axes are logarithmic, so a big name and a small one fit on one chart. A dot well above its neighbours is costly for its volume; one well below is cheap.