I am not at all surprised this bottle is reaching these prices and I can expect it to go higher.
Firstly, it was limited to 89 bottle which is one of the most limited bottles HP have done. I know there was the Orkney rugby club and Maxxim relabelled 12's but they did not come in a box and a nice bottle with a exclusive redisigned label. Also this is a 19 year old, not a run of the mill bottling like the two 12 year olds mention previously. This has more of an appeal to a wider audience as it is something a bit unusaul from HP and collectors and whisky drinkers alike will want to be a part of.
Also the fact that HP allowed two bottles per order, will increase the price on the secondary market. The few people who placed orders prob realised this and got their max no. of bottles. I would estimate that only about 50-60 orders were placed, with many of those for two bottles. Of all the HP collectors all over the UK, never mind the world, for only 50-60 people to getting will obviously again lead to inflated prices on the secondary markets.
Secondly, the whisky itself is a top dram!! I know it was marketed more towards collectors but it is a really great whisky. I was lucky enough to have a couple of drams from a friends bottle (don't worry he opened it not me!

) and can report that it is a complex whisky with a lot going on on the palate. I got hints of heather and of slight peat, with fruit. The finish was long and one that invited you back to the bottle! A top drop
I don't know what the market price of this bottle will eventually but I suspect it will be over £500 as some bottles will be drunk and so on.