Guys, the OP has less than 80 listings (might be over 800 different items, but with variation listings, that doesn't require 800+ single listings) - yes, it's more than the 40 free allocated per month, but not necessarily the cause of all their angst. 

To answer the OP, depends - does that 30% include postage labels you've bought on eBay (they'll include that in your fees and when they calculate that stat chart on your invoices, if that's what you've been looking at) ?

My ebay fees (not including store fee) are something like 13% of my total revenue.

A store would likely be of benefit to you if you want to keep those listings perpetually available and / or add more, $28(ish) a month, more than enough free listings, and a very slight discount on fees.