Most people still think crypto payments means buying coffee with bitcoin. The real shift is quieter and far larger: stablecoins now settle more value annually than many traditional payment networks, and a new category called PayFi is building programmable payment infrastructure on top of that volume. This guide explains what PayFi is, how the plumbing works, and why it matters that a dollar sent on Solana arrives in seconds for a fraction of a cent while the same dollar sent through SWIFT takes days and costs $25 to $50.