This. I haven't had anyone say "sorry, I have bills" but I have gone through some pretty disappointing encounters where I was told someone WOULD commission me, they just don't have the money...and then I see them asking another artist for a commission slot later on the same day or the day after. Usually a more expensive commission slot!
It's just kind of a slap in the face. I'd rather someone didn't say anything to me because I end up feeling like they don't feel my art is 'worth it' but are trying to be polite.