you need to read on the Site Map the differences in benefits for Basic / FEatured / Anchor stores and the monthly fees (and the differences in fvf too)

Stores are only for Buy it Now items, not Auctions, which you seem to favour at present.

if you are only getting 1 or 2 bids per item, then you obviously can gauge the popularity of your items, and could decide on a suitable BiN price.

your listings stay up for 30 days on a store for one listing / or listing fee/ not just 7 or 10days like you have without a store.