Take one truth to heart: If they didn't make any money - they wouldn't have built it.
The manufacturer doesn't pay nearly as much for parts as you or I do. And the assembly process is far more efficient than adding things aftermarket. You can compare a Camaro to a Mercedes - but ultimately what underlines the comparison is that Chevy is a value brand, while Mercedes is not.
No it's not. It has 75 more horsepower...and 300 more lbs. That's all it's got on the Z/28.
If we focus on performance - arguably the Z/28 is more car. The brakes alone on the Z/28 are an $8000 investment (I think Ferrari once offered the exact same equipment as a $20,000 option - and you won't find them on another car this cheap - anywhere)...the wheels, tires; another huge cost.
Now - let's talk about the thinner glass - the COST of removing air-conditioning and radio components. Experimental DSSV shocks? Standard Recaro seats, LS7 engine (that is more expensive than the LSA in the ZL1...)dry-sump oiling?
What about the subtle modifications to the suspension such as bushings and linkages? The fixed-replacement rear seat? All of these things cost more to do.
Regardless of performance...the components used in the Z/28 are far more expensive than those used to build the ZL1.
Also - as I said above: They wouldn't have built it if they weren't going to make money on it...and the car is very special, some might say it's a limited run. Once this generation is over - the LS7 Z/28 will fade forever.