If you sell open source, developer focused software with an explanation, you probably could get away with it. But customer focused, who already goes out of their way to download it (if we assume App Store is more convenient..) should have as little friction as possible IMO. That, and the increased trust.

I also sell, and I do notarize it. Cost is covered by sales, and with a release pipeline the steps are automated, so it's not like it's annoying or anything either.