It all depends on the item. If you are selling SEO services you need to have someway other than ebay to find buyers. The SEO is saturated on Ebay.
The digital books are saturated. Possible to make money but must be done right.
You can sell real physical products all day but remember that ebay fees when all said and done along with paypal run up to 20% which can add up really fast.
Tips: host your own pictures so you never pay for pictures.
Only do straight .99 cent auctions. If you do auction with fixed price, they charge you .50 extra.
If you do those to things then you can list for free and only pay final value fees and paypal fees.
Just as recently as about 5 months ago I was running eBay business for someone selling, knives, paint brushes, and assorted things you might find at flea market or consignment stores. We were doing pretty good until I quit. We just had our differences is all and couldn't work together.
Also I know another girl in my area who goes around thrift stores, bealls, etc these places looking for huge discounts on shoes. She sells nothing but shoes that she buys and resells and she is making around 300 a month. She is using auctiva or something like that where you pay monthly fee but you get to list for free and if your stuff doesn't sell you don't pay.
Anyway hope this helped answer you q. Peace.