SCEE's David Reeves told gamesindustry.biz that there is really no price cut:
"Well, they're not really [cutting prices] are they, because what the US are offering from the 1st of August is a USD 599 version with one game. All they're doing is taking their stock in trade that they've got at the moment of the 60GB model, marking the price down and it will all be gone by the end of July."
He fesses up to a lot of the other stuff many of us have been thinking in this interview.
Basically, the 80GB is cheaper to make (because it doesn't have the PS2's EE chip in it and 80GB is the same price as 60GB). So they're liquidating their 60GB stock and getting a little good publicity out of it.
He even explains the whole reasoning. They cut the EE, thus reducing backwards compatibility. In order to not sound like it's a cheaper machine, they increase the HDD to 80GB, which is almost exactly the same cost to them as a 60GB, and liquidate existing 60GB stocks to sell the cheaper 80GB at the same 600$ price point as before.