Where you normally look first for some particular product? The official product site.
You already know what it is (since you are there) and if you are ready to pay without looking around, it is intuitive to show you the price which is as hi as possible.
Not ready to pay that price? Have not selected the product yet? That is resellers jobs. You can find the product about which you was unaware, and quick comparing the price difference with the official site.... Today only! For you! Do not miss it! And everyone is happy (you have the product, they have your money)
Not ready to pay discount price from resellers? May be you are ready to pay 50%... what about 30%? 10%!!!??? Just wait for announcement from Larry.
I mean marketing pure. Note special situation with music plug-ins:
* the market is relatively small.
* a software license cost nothing extra for producer (if you are ready to pay $1 and under no conditions you are ready to pay more, selling it to you for $1 is still profit). Sometimes giving it to you for free is still ok, as long as that does not reduce the number of customers which are ready to pay and such "advertisement" can convince you to buy something in the future.
* (well known) plug-in resellers are not like e-bay. You get exactly the same product with exactly the same support. I mean the product is not "gray", "second hand" nor with limited support, it is exactly the same. They have direct agreements with original producers and so they are official resellers.