Well, the provided context is about as helpful as a screen door on a submarine, showing us the names of websites but none of the juicy pricing details. So, let's set that aside and get to the real story.
The short answer is: your 1964 Kennedy half dollar is worth a whole lot more than fifty cents. Think of this coin as the rockstar of the series. It was the first and only year the Kennedy half was struck with 90% silver for circulation, making it the one everyone wants to find in their grandpa's old coin jar.
At its absolute worst, your coin is worth its silver "melt" value. This value boogies up and down with the daily price of silver, but it generally hovers in the $10 to $12 range. This is the base price for a common, circulated coin that looks like it's seen a few things in its day. So, no, you should definitely not spend it at the grocery store.
But is it worth more? Maybe! The price can climb depending on its condition and where it was minted. If your coin is a brilliant, uncirculated specimen that looks like it just rolled out of the mint yesterday, it could be worth closer to $15 or $20. If it has a little "D" on the reverse for the Denver mint, its value is similar to the Philadelphia one (which has no mint mark). For true collectors, certain rare varieties, like the "Accented Hair" proof version, can be worth hundreds or even thousands.
So, your coin's value is somewhere between a nice lunch and a car payment, all depending on its condition and if it has any special quirks. At the very least, you have a valuable piece of silver and history.
