Find the cashback break-even point with monthly costs

The essentials

Separate fixed and variable costs to identify break-even spending.
The 2% used below is an assumption, not a current card offer.
Compare within planned spending instead of buying more to earn rewards.

Separate costs by how they behave

Suppose a Korea resident uses the same funding route for overseas purchases each month. A once-monthly deposit expense can be treated as fixed, while a conversion cost proportional to purchases is variable. An issuance charge leaves your account upfront, although a comparison worksheet can allocate it across the months you expect to use the card.

Your chosen time horizon matters. Spreading issuance across a year understates monthly cost if you plan to use the card for only six months. Also distinguish how an already-paid cost affects a future decision. The following is a hypothetical model for starting use, rather than a reconstruction of any particular card’s price list or projected return.

Hypothetical worksheet: $500 versus $2,000

Assume every purchase earns usable rewards of 2%, and variable costs equal 1.2% of spending. Add a $2 monthly funding charge and $5 allocated issuance cost, representing a hypothetical $30 issuance over six months. Fixed monthly costs are therefore $7. All amounts use USD; none represents an actual advertised fee or exchange rate.

Net benefit is spending × (2% − 1.2%) − $7. Break-even is therefore 7 ÷ 0.008 = $875 monthly spending. At $500, assumed costs exceed rewards. To view the worksheet in won, apply one recorded exchange rate throughout, while showing the full issuance payment separately in your first month’s actual cash outflow.

Hypothetical spend	2% reward	1.2% costs	Fixed costs	Net benefit
$500	$10	$6	$7	−$3
$1,000	$20	$12	$7	$1
$2,000	$40	$24	$7	$9

An ordinary Visa card and a payment terminal — Illustrative photographPhoto: Nathan Dumlao · Unsplash License

Replace the assumptions before choosing a card

Actual rewards need not follow the flat rate above. Ether.fi describes progressive rewards by monthly spending and membership. In a real comparison, substitute eligible purchases, applicable bands, refunds and rewards you can actually use. Do not turn an unverified reward into income merely to complete a formula that would otherwise have an unknown input.

Funding larger amounts to reduce fixed charges also changes how long money remains in the account before use. Consider a manageable balance and your actual usage period alongside savings. Finally, compare the existing card’s costs and benefits for the same purchases: a positive result in this model alone does not establish that switching improves your position.

ether.fi — Cashback calculation ↗

Compare the cards in this story

ether.fi Cash Core

RedotPay Virtual

CARD PROFILE	Rewards · first band	Foreign-currency fee	Maintenance / subscription
ether.fi Cash Core	3% on first $2,000/month eligible spend	Base FX ~1% + 0–0.5% margin	Membership $0/year; issuance, shipping and usage costs separate
ether.fi Cash Core · Core entry tier. Standard monthly spend earns 1% after $2,000 and 0.5% after $3,000; EUR bands differ.
RedotPay Virtual	Standard cashback unspecified; Pro separate	Check purchase FX in app; ATM rate is separate	Card $0/year; optional Pro and personal funding-account fees separate
RedotPay Virtual · Issuance payment is not spending balance. Purchase FX could not be reverified from the readable public fee page.