You open a new card for the $200 welcome bonus while carrying the $4,100: the bonus costs $385.51

Same debt as the earlier examples: $4,100 on a card at 18.9% APR, no new charges. Paying a fixed $230 a month, on time, takes 22 months and $751 of interest, $4,850.59 total. This one adds a mailbox offer. A no-annual-fee cash-back card — the Chase Freedom Flex is the usual example — pays a $200 bonus after $500 in purchases in the first 3 months, with 0% intro APR for 15 months, then 18.49% to 27.99% variable. Those are the published terms, checked November 2026. Two hundred dollars for spending you were going to do anyway sounds like free money. The question is whether the spending was actually spending you were going to do anyway — and what happens to the $230 a month while the new card is open. Scenario A: leave the offer alone — the boring baseline You pay the card $230 a month and ignore the mailbox. The card finishes in 22 months, $750.59 of interest, $4,850.59 total. Nothing in this scenario is a trick. It is the number every other scenario below has to beat — and the bonus has to beat it after counting the spending it caused, not before. Scenario B: you spend $500 to earn $200 — the bonus costs $385.51 You open the card and buy a $500 item in the first 3 months to trigger the bonus. The $200 arrives as a statement credit, so the new balance is $300. Your $230 a month is already committed to the old card, so the new card gets only its $25 minimum. The 0% intro covers it — $300 at $25 a month is gone in 12 months with $0 of interest. Here is what that costs. While the new card takes $25 a month, the old card gets $205 instead of $230. It finishes in 23 months instead of 22, with $836.10 of interest instead of $750.59 — $85.51 more. Add the $300 you still owe on the item after the credit, and your total cash out the door is $5,236.10 against the baseline's $4,850.59. That is $385.51 more, for a $500 item you had not planned to buy. The bonus did not pay for the item. The bonus paid for $200 of it, and the diverted payments plus the other $300 came out of your pocket. You spent $500 to earn $200, and the earning cost $385.51. Scenario C: you spend $1,500 "to make sure" — the bonus costs $1,565.19 Maybe $500 feels too close to the line, so you put $1,500 on the new card in the first 3 months — some of it planned, most of it not. The $200 credit leaves a $1,300 balance. Same $25 minimum, same $230 a month split the same way. The 0% intro lasts 15 months, and minimum payments barely dent the balance: after 15 months of $25 payments you still owe $925. Then the rate jumps to 18.49% — the lowest end of the card's published range, the kindest assumption available. The old card finishes in month 25 with $863.32 of interest. Only then does the full $230 swing over to the new card, which finally dies in month 28 with $152.46 of interest of its own. Total interest across both cards is $1,015.79 against the baseline's $750.59 — $265.20 more. Total cash out the door is $6,415.78 against $4,850.59: $1,565.19 more, for $1,500 of stuff. The bigger the spend you use to chase the bonus, the more of the bonus the interest eats — and the 0% intro does not save you, because at $25 a month you were never paying the balance down fast enough to finish inside it. Scenario D: the honest way — planned spending, paid in full, $200 to the old card The bonus is real money, but only under two conditions: the $500 is spending you were already going to do, and the new card is paid in full every month from the cash that spending would have used. Put $500 of groceries on the new card, pay the new card $500 from the grocery money, redeem the $200 as a statement credit on the old card. The old balance drops to $3,900. At $230 a month it finishes in 20 months with $673.01 of interest — $277.58 less out of pocket than the baseline, two months early. Same card, same bonus, same $200. The difference between Scenario B and Scenario D is not the card. It is whether the $500 was already leaving your wallet, and whether the new card ever carried a balance. Scenario E: wait until the old card is dead, then take the bonus If you cannot trust yourself to pay the new card in full — and while you are carrying $4,100 at 18.9%, that is the honest assumption — do not open it yet. Pay the $4,100 off first: 22 months, $750.59 of interest, done. Then open the card, put $500 of planned spending on it, pay it in full, and pocket the $200 as cash. The interest stays $750.59 and you are $200 ahead, with no diverted payments and no second balance. The bonus was never the problem. Opening a second line of credit while the first one is still bleeding is the problem, and waiting 22 months costs nothing — the offer is the standard one, and it will still be there. Run your own version of these numbers — same $4,100, same $230, your own bonus offer and your own spending — in the calculator: https://alapha888.github.io/irregular-income-debt-baseline/ The rule that survives all five scenarios: a welcome bonus is a discount on spending you were already going to do, and a tax on spending you were not. The $200 is real, but it is the last number in the story, not the first — the first numbers are the $500 of new spending, the $25 a month diverted from the old card, and the $85.51 of extra interest that diversion buys. If the spending was planned and the new card is paid in full, take the $200. If either of those is false, the bonus costs more than it pays, and the card that pays you $200 is the most expensive $200 you will ever earn. At $300 a month the card is gone even sooner, in 16 months with $553.80 of interest.