Same thing happened to a friend of mine who was living at De Fenwick in Wanchai - they upped the rent by 30%. It seems to a common phenomenon since the housing market started improving. The only thing I could suggest would be to seek a flat share, either in the property pages (
www.scmp.com) or through forums like these. I managed to set up a similar arrangement in the late 90's when I was spending time between HK and the Middle East. Works well, if you can trust the people you're sharing with.
If your serviced apartment was costing $850/day ($25,500/month), you could split the rental with one ot two others and get that down to around HK$6,000/month, or HK$200/day.
Even places in Island East are only offering discounted rates for a studio at HK$16,800/month.