A toolhead that rattles around on a Dillon 650 is a common problem. The cast aluminum toolheads that Dillon sells are somewhat undersized compared to the slot they go into. This up and down play in the toolhead can have several detrimental effects on the consistancy of your reloads.
So thats the $30 option. There's also another option that costs little to no money and works pretty well, shimming the toolhead. This isn't quite as good as the helicoil screw system, but it's close.
I prefer to place the shims on top of the toolhead so that it is held down. Note that this will likely require adjusting your dies, which are most likely set for the toolhead pushed upward. You can shim the bottom instead, but in my experience, this leads to a slightly angled toolhead which will impart a slight angle to the die in station 4.