A higher bracket rate applies only to the dollars above its threshold, so every extra dollar earned raises take-home pay — the apparent cliff comes from mistakenly applying the top rate to the whole income.

0100k150k0100k150kTake-home at the point income reaches the second thresholdTake-home at the point income reaches the first threshold
Take-home pay, taxed bracket by bracketTake-home pay if the top rate hit every dollar
44000 USD
5000 USD
Extra money actually kept from the raise$4,215
Change in pay if the new top rate were applied to all income$-500

Interactive artifact by Delineo