I had a similar experience. My RX330 windshield cracked all by itself while the car was sitting in parking position under 110 Fahrenheit degree in September.
On day 1, Saturday, a very hot day and the car was in parking position outside the garage, the crack was very smooth and ran about 5 inches down starting from the very top, on the driver's view side.
On day 2, nothing changed when I drove to Church. After Church, I observed the crack got extended toward the small mirror running like a snake. Since the cracks now made curves, the crack was not smooth anymore near the snake like curves
From then on, it started cracking snake like toward the bottom. I am not sure why it did that way instead of a straight line.
I brought the car to Lexus, they did a pen test (pushing back and forth making the crack now looks... ugly) and concluded the cause was by rock hitting
Saying there was not much they could do, they did not do windshield replacement and that I had to go find a shop myself
I consulted my insurance and they referred a shop that they had partnership with. The shop specialized in auto glass and they seem to pride in what they do. That shop replaced the windshield for a little over $400. That was the final cost including the 3 1/2 hours of labor (as saying in the invoice) (although it only took them less than 1 hour; since I stayed at the shop watching them replacing the windshield). The windshield replaced was a Lexus windshield; the shop ordered from Lexus. When I asked for the cost, they said $400+ saying Lexus windshield is expensive acted like $400 is a lot of money. I mean, they sounded like $400 is a big order that they don't normally charge on other cars. My Lexus dealer didn't say anything so I did not know how much it would cost. I did feel great because I prepared in mind that it would cost a lot
I ceased liking Lexus starting from this event and I am very surprised to learn that it cost you that much replacing directly from Lexus.
