Yes agree with Nick on this one.
I think you’ll also find that you are likely using a measure here for Unit Price instead of a column.
So there’s a few places where this is falling over for you.
You need to use FILTER here, which is very easy to do and gives you a lot more flexibility in the calculations you are doing.
I actually use FILTER on nearly all occasions just because I know that it’s much more versatile. It’s really important to actually understand what FILTER is doing by iterating through the table that you give it. This is a very key concept to master early on with Power BI.
Please check out the below tutorials to learn more around this.
http://portal.enterprisedna.co/courses/108877/lectures/2000601
http://portal.enterprisedna.co/courses/108877/lectures/2000638
http://portal.enterprisedna.co/courses/108877/lectures/2000639
See how you go working through these ideas and techniques.
Thanks
Sam