Quick notes on comparing crypto debit cards

A short list of things I keep relearning every time I audit another crypto debit card. None of this is investment advice. It is just the stuff that surprised me when I started comparing cards for the directory at sweepbase.net.

Headline cashback rates are almost always capped

Every issuer leads with a headline number. Four percent, five percent, sometimes eight. Read two more screens down and the number is capped per month, or requires a staked position worth several thousand dollars, or applies only inside a merchant category that excludes everything people actually spend on.

The practical rate on a typical monthly basket of groceries, transport, subscriptions, and a few bills rarely clears two percent. Sometimes it is closer to one. That is still a reasonable return if the card is free, but it is not the number on the landing page.

The FX fee is where the real cost lives

Many cards advertise zero FX fees on the network rate. What the fine print often adds is a one or two percent spread on the stablecoin-to-fiat conversion happening before the Visa or Mastercard leg of the transaction. That spread is an FX fee by another name.

If a card is going to be used abroad or for merchants priced in a non-local currency, the combined spread is the number to check. A zero-FX card with a one and a half percent stablecoin markup is identical to a one and a half percent FX card.

Staking requirements are a separate cost

Tiered cards tend to require a locked position in a native token to unlock the higher cashback tier. Two things matter here. First, the token can lose half its value in six months, and the cashback boost does not compensate for that. Second, the stake is capital that could be earning something else.

I treat the stake as an opportunity cost equal to whatever a short-term treasury would yield on the same amount. If the cashback gain minus the opportunity cost is positive, the tier is worth it. Often it is not.

Self-custody changes the risk profile, not the rewards

A self-custody card charges from a wallet you hold the keys to. The issuer never has the funds. That is a real security improvement, and it changes what happens if the issuer goes bankrupt.

It does not usually give better cashback. It does not always give lower fees. The pitch is custody risk reduction, not economics. People who want both should compare self-custody cards against each other rather than against every custodial card on the market.

The boring cards usually win

A free card with a flat one percent cashback, no staking, no tiers, and a known FX spread will outperform most high-headline cards across a full year. That is not a satisfying answer, but it matches what the numbers show when the calculator at sweepbase.net/calculator is run against a twelve-month basket.

The whole comparison tool is at sweepbase.net if the numbers are worth checking against a specific card.