I'm not sure exactly what you're asking when you say "Is it worth it?" but the personal stores are like any other venture in that your success is related to your efforts.
An Eden Personal Store requires you to have a domain, which costs about $8-12 per year. We offer free hosting, but you can choose to host the store yourself. So the only real money cost is the domain. But a store is only what you make of it. It isn't realistic to think you can set up a store, add some products and a banner, then walk away and wait for the affiliate checks to roll in.
If you want to make significant commission, you would need to personalize your store, find your niche, and promote your store to your targeted audience. If you have a blog or site already set up with an audience, you can gear your store toward their wants and needs.
Read more info on Eden Personal Stores here
. Email email@example.com with questions.
On a somewhat related note...
Perhaps you'd like to consider onsite personal stores which are simpler to setup and are located on EdenFantasys. Check out the onsite stores that by other community members. If you'd like to have one yourself, just send a request with your username and the store name to firstname.lastname@example.org. Be sure to have a unique idea and name for your store.