Yup... price is certainly a reason, but its not the only one (though the fact that production cost of one Dragon was probably like 10X to 50X that of an Excalibur).
Reason 1 - Cost Efficiency
The Dragon, with its nuclear engine, ramscoops (eternally self-refueling so no limit to afterburners or need to dock/refuel for jumps), cloak, and gun loadout (charging fission cannon or whatever that special charge-gun was) probably made it like so expensive that you could make a dozen excaliburs in comparison.
Which is why, as they put it in the WC Saga fan-game, they put noobies into Arrows (or whatever light or cheap medium fighter they have). The Kats realized the same thing... no matter how well trained you are, on your first real combat mission there's like a 50% chance you're not coming back. (your chance gets far better with each mission due to experience, so unless their desperate for pilots, its skill PLUS experience = better ship.)
Which is why the Kats tend to have lots and lots and lots of cheaper ships. MOTIVATION TO SURVIVE.
Reason 2 - Possible Pilot Killer?
Blair and the Black Lightning's super-soldiers were teh only ones to really pilot the Dragons too... so quite possibly the ship was "too good" for most normal humans to pilot.
Nearest comparison of what I mean can be seen in Getter Robo - Neo vs Shin. In essense the ship could be a pilot-killer... the thing is so fast and maneuverable that even with the high-tech flight-suit and life-support gear, that the ship's g-capacity (in turns and acceleration/deceleration) would injure if not kill most pilots. (anyone who's seen teh first ep of that anime has seen how even an excellent pilot can crasn'n'burn if subjected to enough G)
Most of the Lance were genetically engineered super-soldiers... and as such, were enhanced with superior strength and tissue resiliance (though muscle has little to do with it. It has more to do with cell density, tissue elasticity, etc. )
Good example is Seether's fav maneuver. That drop'a'mine and ride'its'shockwave type maneuver could easily cause internal bruising if not capilery ruptures and/or organ damage in older pilots or gifted-but-physically/biologically-weaker pilots. God-like pilot skills won't save you if the moment you're in a 4G turn half your internal organs decide to break loose and dance around.
You through something like this (reason 2) in with reason 1 and you end up with a good way to loose a war extremely quickly. (half your pilots die due to lack of experience, and most of the other half die cause they couldn't survive the first high-G maneuver they try.) Its why they stick you in a simulator long before they let you into the real thing.
POSSIBLE EXCEPTIONS
There's a limit to what inertial dampeners and simple spring-based or sponge-based shock absorbers can do (short of the wonderful magical super-high-teck ones in Star Trek).
In a few sci-fi's I've seen them have the pilot submerged into some kind of thick viscous fluid, often with a breathing tube or some breathable fluid (like amniotic fluid... the liquid stuff babies "breathe" while inside their mothers) cause the thick fluid acts like one giant shock absorber. Problem is that this method is expensive and difficult to do... which is why you often seen robotic drones (no human pilot or remote piloted) or bugs (grown ship/pilot combinations) or variations of the two (non-physical telepathically operated controls, thought-reading controls, etc... ).
