There are some great high tea choices in Perth, but for value and sheer quantity of yummyness, I love the high tea at the Vines, Swan Valley. Everything tastes really fresh and there is a great selection of hot and cold items. I think this picture of what's on offer says it all!
Also the C Restaurant in Perth. A great high tea, with a excellent view. The restaurant is set high up in the building and is a revolving restaurant where your view is ever changing. Great service too.