The instant buy applies its 0.50% markup to the price, so you actually transact at
$64,503.31 rather than $64,182.40, and $5,000 converts to 0.0775154 BTC. The maker
order transacts at the market price and charges 0.10% on the fill, leaving 0.0778251
BTC. That gap of 0.0003097 BTC is worth about $19.88 at the same price:
the $25.00 spread minus the $5.00 fee, give or take rounding on the fee basis.
Scale it and the pattern matters more than the single trade. Twelve monthly $5,000 buys
cost $300 a year through instant buy against $60 a year
as a maker: the same $60,000 of exposure, $240 kept. The honest counterpoint is that a
limit order can sit unfilled while the price runs away, and missing a 3% move on $5,000
costs $150, far more than the $20 you saved. Convenience is not always the wrong
purchase. It should just be a deliberate one.