It has a sort of weird appeal. Because it's silly.

On the other hand, it's silly.

And it's expensive. If it was 75 quid, it might be worth it for a laugh, but it's 300! Three hundred actual pounds.

If you want a BB firing bolt action military-style rifle, then something like a CZ47 or Haenel 33 would be my choice. £300 would get you a very nice one. It won't lose its value. It is unlikely to go wrong. If it does go wrong, you can fix it. None of which necessarily applies to the Mosin.