It's hard to say if that is a good deal or not.
To a purist, the interest in that grenade changes. That is not an accurate-to-screen-used-prop Hales. The fragmentation tube has a variant cuff/lip by the windvane. A purist won't want it on their saber but maybe as a variant historical specimen of the original item archived as an example of the originally intended use/purpose of the item. It, I assume is also somewhat rare among No.3 Mk1's, but I don't know that. I also don't know pricing for the pure WWI or British Grenade collectors. I would be surprised to see it not sell for that amount, mostly for the variant and condition reasons to non-Star Warsy collectors.
The brass plate at the end of the central shaft is also wider than the screen used hero prop. The plate appears to completely cover the lip of the fragmentation tube, the tube which is already wider than typical.
Its difficult to know the actual shape of the fragmentation tube.