| This is a really interesting discussion for me to follow, as I'm actually the guy at Amazon who's responsible for the customer experience in the Musical Instruments store. We argue about the best way to display things like shipping charges and who's selling an item all the time here, so it's always helpful for me to see real users commenting on the way the site works. Clearly, we still don't have it exactly right because people still get confused, that's obviously our fault, not yours.
The initial question here was how to figure out what the shipping charges are, and then it devolved into who the heck is selling this or why did the link change. In fact, Amazon.com isn't currently selling this item.
Basically on Amazon there's all this stuff you can buy (basses, TVs, Hannah Montana action figures etc.), and some of the products are sold by Amazon, meaning we buy it directly from the manufacturers, we keep it in our fulfillment centers (warehouses), we get all the revenue when a customer buys it, and we ship the product to the customer and take returns and do the customer service after the fact and all that stuff that a retailer does.
On most product in the Musical Instruments store, there's also several other retailers listing offers. This is good for customers because it lays everyone's price right out there for all to see, and it means that the thing you want is usually in stock from someone.
On any given product detail page, you'll see the big Add to Cart button on the right, and clicking that will mean you're buy from whichever merchant's name is next to the big price call-out next to the image. Which merchant that is is dependent on who has the best price and availability combination at the time you hit the page.
If that happens to be Amazon.com, the shipping is almost always going to be free. in Musical Instruments, that's our thing and so far we're sticking with it (no absolute promises here, I'll bet if we start selling grand pianos we'll charge some shipping). Many of the other sellers also do free shipping most of the time. If it's someone besides Amazon who has the best offer, then the price + shipping will be listed right above the add to cart button.
You could also buy from some other seller you like better by looking below the add to cart button for their offer. A link to a single page seems to change results over time, because at any given point in time, a different selelr might be owning that Add to Cart button. ON this page you linked to for example, there's several sellers who all have the same price, and free shipping, and they're all in stock. It's a tie, so the add to cart button rotates between the sellers. You can still choose who you want to buy from under more buying choices. | 
thanks again
