Absolutely, in many cases, shipping fees are actually a combination of shipping charges, packaging costs (boxes, tape, labels, bubble wrap, etc.), eBay fees (listing fees, selling fees), paypal fees (like 2.7% or something of the total money received) and that's only if the selling is trying to cover costs. I think somewhere around $20 (+/- $3) is reasonable as a shipping fee for a bowling ball. The ones I have a problem with (and refuse to place a bid, just on principle) are the auctions trying to charge $30, $40, or $50 for shipping fees..
As far as why a seller would offer free shipping on their own site? Well, to attract business! If you buy a ball there, then maybe you will invest in their drilling services, or buy a set of finger grips, or some cleaner.. who know. If nothing else, increase traffic to their site.
S^2
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-Was Chris Berman trying to grow a moustache on MNF, or was that pine tar?