Did you know there is no default way to set up Paypal to charge shipping costs based on quantity? You can set up a little in your Profile section, but that only lets you have up to 5 options. If you want to charge straight by quantity, it’s not easy to figure out how to do it. I found this site very helpful: https://www.x.com/developers/community/blogs/ppmacole/shipping-prices-website-payments-standard
Specifically, this part:
“If you’re using the Button Factory, you’ll need to set the single shipping price in the “Shipping” section (see the Single Shipping Price section above). Then, you’ll need to go to the “Customize advanced features” section — it’s going to be down towards the bottom of the page.
Next, find “Add advanced variables”. Again, it’s going to be down near the bottom of the page. Click the checkbox next to it, and in the box below, enter (without any spaces), “shipping2=(price)” — of course, change “(price)” to whatever your incremental shipping price is. So, for example, if your incremental shipping price is $2.50, enter “shipping2=2.50”. This is how it should look when you’re all done: