First of all, webpageoutlook.com and all other sites like it are worthless. Other than that, I agree with you that the site is overpriced.
My main concern is how long will it take you to move that inventory? If the site is only making $100 per month, either he isn't selling much or the items are very low margin. Also, make sure that he isn't trying to unload it on you at retail price, since it doesn't sound like he has been very successful.
What are your plans for the site? Do you feel like you could keep making $100 per month with no work, can you ramp up sales easily due to your past experience or other businesses, or is this something new?