No, I said: "if I could, why would you not?" (because you'd said "I suppose you could, but I don't think I would"). I meant -- if a native speaker wouldn't use it by himself, why does he say that a non-native speaker could use it?OK, but at post 3, you say "If I could [use 'with'], why could you not?" That's like saying "If a non-native speaker does it this way, why don't the native speakers?" :
I didn't know it was not attested. I just found it logical, as I said in #4, and I found some examples in GoogleOf all the prepositions that you could have chosen, why did you choose "with"? Why do you say you could use "afford it with my salary" when that expression is not attested?