Ebay really sucks you in. I find it incredibly interesting seeing what you can find on ebay - really obsure stuff.
To be honest your looking for a temporary fix / high / fill. Consumerism grabs us even when we are sat at home. If your board dont go on ebay. Chat online or build your own website - a good site whcih is easy to use is
www.streamline.net
Try and do something that occupys your mind. Or if you really do have to buy something - buy a really good book off ebay. And when it gets delivered lock yourself away and read it until your finished. Then you can 'reward' yourself with another book.
This way at least you are gaining knowledge from the experience - which is priceless and always a good buy. Just be careful not to get carried away.
The only way to get away from it completely is to disconnect or 'Ban' the site from your PC. But really you will find a substitute. Think about why you are buying things. Is it because you want to look a certain way, or you like nice things. Are you always comparing what other people have and what you have? The art of comparision is an age old desire that spurs people on. Try and understand why you are buying, what you are buying and if it is absolutley essential for your better quality of life. If it will give you years of enjoyment or just a few seconds.
I can recommend a great book 'Mans Search for Meaning' by Vicktor Frankl. The book has stopped being published so if you can find it anywhere ebay is the place and I'd love to know if you get a copy as it took me weeks to find one.
Its worth reading as he was a revolutionary phycologist and the book changed my perspective on things.
I still shop on ebay - and I too am a compulsive shopaholic, but I can control it. I only shop for what I need and if its essential. Good luck and I hope this helps