Yeah, I think you have to be level 7 to start doing scents. I could be wrong but I know it's a higher level than 3.
As for the hours, yeah that might be the issue. As I said, just when the employees are leaving, people are starting to really start buying which is why I can't close when my employees leave. It takes that long for the guests to get their buy bar full. Of course, I do have those that buy through out the day too but not as many as just after or right when my employee is going home. My advice is, if you haven't already, try staying open for a few hours after the employees leave and see if the sales don't start popping up.
I think the most expensive thing in my store is $225 and my cheapest is $5 so that's the range of prices. They all seem to sell pretty good so it's funny that our experiences are so different. For you, the customer wants mainly the most expensive, which takes longer for them to decide to buy. For me, they buy at any price so the buy times vary.
EDIT: Another thing is that I have a wall speaker and some sofas for the guests to sit on. I have a swing outside mainly for my own kid to use (which nobody ever does, including him) but other than that, I don't have anything to distract them. I've yet to catch one of my guests dancing and have only seen my employee dance once which I put the kibash all right away.
I'm gonna upload my store so you can download it and see what it's like, if you want. But be warned, it's very basic on the inside and has almost nothing but collectables so if you're going for a collection challenge, this could be a help or a hinderance depending of if you want to find these things for yourself. lol I'll post on here when I get it uploaded. That probably won't be until tomorrow.