Electricity is cheap only is some areas of the world. Some people pay dearly for it and as such it impacts them more than others.
And can we please lay to rest the notion that Tonga is the same thing as Tahiti? It's not. We've been over this many times. While many paper specs are the same ( shader count, texture units, and ROPs ), Tonga shares a lot with Hawai'i. It has 8 async compute engines compared to Tahiti's two, quad-shaders instead of dual-shaders, and bridgeless CFX over XDMA. It may be a small revision, but it's a revision nonetheless and is its own silicon. If you say Tonga is the exact same as Tahiti, then you should say Haswell is the exact same as Ivy Bridge.