Demand Curve Price not perfectly elastic I'm trying to make the argument that our Sales go up when prices for all our Products are 30% off. Which I believe should be our new Regular Price. but our Demand Curve doesn't support this. Should I be setting up the demand curve differently? on a per product basis? or package size?


I sell our food product in different package sizes
2oz, 4oz, 9oz , 16oz 3.5lb
Normalized the time our products were at that price.
Counting your quantity in ounces makes sense, I wouldn't change that (I assume each point is a total sales/price combination at a given time?). 

If you want to look at the impact of a percentage change in your price, you should take the logarithm of price. A .3 change in log(price) is roughly equivalent to a 30% change in price.

That said, you do in fact see a downward slope on your demand curve, which indicates that a drop in price is correlated with an increase in sales, although it's a general negative relationship and there's nothing special about 30% in particular (I wouldn't expect there to be!). So you're pretty much showing what you want (discounting issues about statistical significance, or causal identification - if these prices aren't set randomly this isn't technically showing you a demand curve).