These are not very well-known in the US but they do have their fans, and out of the few Hayman bass drums made, not many were probably 24, so just on that alone I'd expect to pay around $800 for these - more perhaps if the condition was exceptional and the color was nice.
About 5 years ago I bought a 22, 12, 12 and 16 in the dark solid blue which was missing some parts (hard to find) off ebay and paid less than 500 for them. I managed to get one of the single tom holders to replace the very awkward double tom holder. I still have not gotten the set up and running. They are cool drums.
If I found a Hayman set with original wrap and hardware in those sizes, I'd be all over that for $800. That being said because of their rarity in the USA you can sometimes sneak a really good deal on them.