Welcome to FT - well, it depends on whether you are using eBay's discounted shipping partner services, i.e. USPS or UPS ground vs. retail rates locally, mostly not qualified for the flat rates. High volume sellers sometimes have choices for using their own negotiated rates, i.e. UPS Surepost (last mile delivery by USPS) - FedEx & DHL have similar arrangements.

From a quick lookup of our eBay purchase history - the above rates are somehwhat "low" - i.e. Costo's Kirkland 22"+ roller at 13+ lbs shipped weight was quoted about $30, but actually higher by about $10 taken to USPS for actual postage due (even when taking into account eBay's discounting/negotiated flat rate deals ... sometimes) If you are near a Staples or authorized UPS shipping outlet, and/or postal office - as suggested, take your items & get an exact price quote.

Keep in mind to add any packaging or boxes, bubble wraps & tapes, etc. and, of course, calculate your selling costs including fees & paypal's - there are forums dedicated to that. Here's one link to their counterpart on Amazon - happy reading & selling