This is almost too vague of a question, because CTR is really dependent on a ton of variables, such as:
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Perceived value of said "bonus"
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Industry served
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How specific, or broad your targeting is
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Do you cap your impressions?
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Branding and brand recognition (does it look familiar to the viewer - do they recall your message your brand, what your product is all about?)
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The design/interactivity of the ad
Remarketing campaigns can vary significantly on those factors (and probably others), but if you can achieve 1% that would be pretty impressive IMO. Realistically, most the remarketing campaigns I've run (healthcare industry) end up .01-.75% CTR.