Fee estimation in a Bitcoin wallet is a user experience problem as much as a technical one. Users see a transaction stuck for hours and blame the wallet, regardless of what caused the delay.
Bitcoin mempool fees are not predictable. During normal periods, a 10 sat/vB transaction confirms in minutes. During Ordinals inscriptions, market volatility, or halving events, the same rate may sit unconfirmed for hours.
If you're setting gasPrice the same way across Ethereum, Polygon, and BSC, you're going to have problems. EIP-1559 fee mechanics are network-specific, and the right approach for Ethereum mainnet is wrong for Polygon and mostly irrelevant for BSC.
Bitcoin fee estimation is one of those problems that looks simple until you handle it in production. Simple sat/vB tiers break down quickly when you need to handle stuck transactions, vary by transaction type, or send hundreds of transactions efficiently.
Bitcoin transaction fees confuse even experienced developers. They fluctuate wildly, different services give different estimates, and getting them wrong costs real money.