Well, perhaps true for that first seller (regarding their shipping fee), which seems to move enough product through Amazon to be large enough to sign up for a higher-tier "professional" type of seller account with Amazon. If so, then they could have had the option to offer "free" shipping.
The second seller though, offering the disc for a "more reasonable"
$399, I'm sure they had no say about the shipping fee. That's dictated by Amazon. A small-time seller like that one (only 41 sales feedbacks) can't offer "free shipping", even if they had wanted to. $2.98 is standard and set in stone for them.