I don't understand the logic of your result table. But to match the Date from the Sales table with the interval in the Price_List table you need to use the Intervalmatch function. Try the script below and then add two table boxes for the two tables that are created in the script.
Note, the INLINE loads are just examples. You can use your excel file as a source instead.
Date(Date#(left(price.start,10),'YYYY-MM-DD'),'YYYY-MM-DD') as price.start,
Date(Alt(Date#(price.exp,'YYYY-MM-DD'),makedate(2099)),'YYYY-MM-DD') as price.exp