check the gm parts catalog for hp ratings. i accept that they're conservative...so the lsx is conservatively rated at 2500 hp. whatever an ls2 can withstand for 8.xx seconds, and lsx can handle many times more, and endure much longer. how often do those engines run and last?
the high cost of first run ls1 blocks demonstrates the difficulty in making it. ls3 heads cost $800 new, while gm's own cnc ls2 heads are $2000. lowering mfg costs account for the ls1 vs ls2 price difference. and the difference you quoted is still 50-60%. when mfg will work to cut pennies, $300 is not insignificant.
you obviously have no concept of design vs materials. engines today are designed much better captain obvious. and 99% of aluminum blocks use iron liners - you suggest that aluminum makes it durable. steel has a higher fatigue strength than aluminum - it will last
infinite cycles below ~50% yield stress. aluminum will continually lower its yield stress and fail at a predictable number of cycles. high stress parts are still steel - rods, main caps, fasteners, valvesprings etc. they use aluminum when they can get away with it. will cars today last as long as older cars?
all the ribbing designed into aluminum parts to increase strength and diffuse noise. mfg use coolant to dampen combustion noise. the lighter the part, the more noise it radiates. you'll sometimes find steel weights on suspension arms to dampen resonances. i was talking to a quiet steel rep recently, and he admitted that while the elastomer dampens high frequency noise, you still need mass to dampen low frequency noise.
the movement to aluminum in cars is a direct result of increasing minimum creature comforts, 'safety' devices, economy and size. the aluminum lobbies have a lot to do with it, as well as consumer perception.
so in my automotive engineering mind, from a material standpoint cast iron is just as viable as aluminum...just as i believe 2v are better than dohc in street cars. even aston martin says that 2v are an advantage in racing, and the ls7r wins motorsports engine of the year. a cast iron block ohv v6 imo is on par with a dohc aluminum v6.
c'mon, this is sophomore thermodynamics. even high schoolers learn that temperature and pressure are related - boyle's law. a thin section of material will conduct and transfer heat SLOWER than a thick section. and the boundary impedes heat again. compression ratios above 10.1 DO lower mechanical efficiency, but can be compensated with thermal efficiency. do you understand the distinction?