Stats vary from source to source as well. For example, the latest Residex report states last yrs cg rates for Killara units as 8.84% and Lindfield 8.53%, so I'm not sure where the 54% rates are sourced from.
You also need to remember that cap growth rates are affected artificially by new dvpts in the area, particularly those of a high end nature. For example, Lindfield has some pretty upmarket $1.2m+ units in its new Mirvac builds (see here
http://www.realestate.com.au/cgi-bi...r=&cc=&c=71260539&s=nsw&snf=rbs&tm=1244794033 ) which, when compared to the traditionally older units in the area (see here
http://www.realestate.com.au/cgi-bi...r=&cc=&c=71260539&s=nsw&snf=rbs&tm=1244794033 ) serve to skew the growth figures somewhat, as you can appreciate. Always undertake further investigation when growth rates appear to be too good to be true, and you'll begin to see for yourself why they may be misleading or deceptive.
Best of luck with your purchase- I quite like these 2 suburbs myself but would only buy units within walking distance of Lindfield or Gordon and Killara stations. With many baby boomers downsizing in the area, yet still wanting to remain close, such Mirvac apartments will have a market, despite their pricey tags. Picking up an older unit in the $500K's and renovating it could well be a good start to one's portfolio if you buy well. Best of luck!