Does "with your pay" exist?
Solution 1:
I like the coat very much. —But can you afford such an expensive coat ____(on/ with) your pay? which option is right?
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It's certainly 'on'.
-But can you afford such an expensive coat on your pay/ salary?.
-I don't know how he can afford a new car on his salary. - Cambridge dictionary
Google Ngram Viewer shows 'afford on' but doesn't show 'afford with'.
Solution 2:
Both are correct.
Speaking as an Australian, I can say that both of those sound correct to me; if there’s a regional difference between British and American English, we’ve evidently gotten the best of both worlds here.
I think there might be a small difference in meaning, though; “on your pay” is a bit more referring to your ranking on a formal pay scale -e.g. “on apprentice wages”, whereas “with your pay” might be referring to your physical payments “going to the bank with my pay in my pocket”.