It depends on how good your stuff is, and what it is. Different categories have different sell rates. Also, the store/s you choose to sell at makes a big difference.

For me personally - selling a set of textures has never made as much as selling a mesh clothing item (but I am primarily a modeller, not a texturist). I have never made as much here as at Poser Pros, and my Daz sales eclipse both of those by a long way. If I release a new clothing set, I definately make more than $100 p/w for the first month or two. I've been in this business for years and do have a reputation for good quality stuff. It's harder for newer modelers to make as much simply because their quality and standards are unknown. You also have to realise that sales do taper off at some point so you need to be releasing new stuff to keep the flow going.

Have you set anything up for Poser before? It's a lot more complicated than just modelling/texturing. There is quite a bit involved, and it's very important to get it right.

I always suggest making and giving away freebies for about a year before getting into the stores. It let's people see a good range of your work, gives people a chance to see the quality of your work, and it gives back to the community.

Hope that helps!