OK. Let's assume that it costs $1.50 - $2.50 in electricity/equipment to make a bitcoin.

Why don't I give up work and start mining tomorrow?

There's labour costs / opportunity costs.
There's the accumulation of knowledge.
Lack of hardware supply? (supply drops, price is higher)

There's more cost than just the electricity at the moment but eventually the electricity costs will be the main factor. I don't think people are factoring in the really big costs - the opportunity cost being the greatest.

Seems possible that $17 might be close to the cost of producing a bitcoin given the current conditions (opportunity costs, hardware availability, knowledge acquisition, electricity) and perhaps that's why it has stabilised.

My comment regarding kWh per BTC was misleading.

See this post for a similar discussion regarind mining cost / price correlation...
http://forum.bitcoin.org/index.php?topic=23360.60