Don't remember what I paid for it, but I bought some of the Fiocchi .455 about 4 years ago. Seems like I got it from SG ammo. I chronographed it in my old MKVI Webley with 6" barrel. It averaged a very leisurely 554 FPS. Looks like CIL ballistics, if as fast as published, exceeds the Flocci ammo I tested by quite a bit.
BTW, throat diameter on my old Webley measures .450". A bit tighter than many might expect. Some other Webley owners have reported their guns have throats measuring .450" also. The .452" cast bullets and .451" plated bullets shoot well in my old gun. I wondered if my Webley would even be on the paper at 15 yards, but it did better than I expected.
A pulled bullet from a factory Fiocchi round measured .454", and weighed 263.4 grains..