Are the following sentences natural to a native ear?
1. How much does it cost for a bag of these strips?
2. Are you not wishing that you had a few more days of vacation?
3. She never tried to raise her voice when we have/had discussions before this week.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.