Live gas prices across Base, Ethereum, Arbitrum, Optimism, and Polygon with USD cost estimates for a transfer, an ERC-20 send, and a swap — keyless, one call, all chains. Per chain: gas price + EIP-1559 base/priority fee in gwei, native-token USD price, 15s cache. L2 figures are execution-gas only (L1 data fee excluded, flagged in findings).