I can understand it as tech advancing in the Golden Century. I mean an Clantech LRM shouldn't require magic minerals to be half as heavy as an IS tech LRM, it just benefits from hundreds of years of advancement. Just like a computer from the 90's is smaller and has more power than a computer from the 80's. Or like how armor can improve from BAR 5 to BAR 9 to standard to ferro. New methods of manufacturing without an entire arbitrary 'tech base'.
But I assume that 'tech base' is like FASAnomics. It's just something cooked into the game.
(and yes, I think the Improved PPC and Enhanced PPC should be IS tech base. The Improved PPC is going to be more expensive than the standard PPC, so there would be that factor.)
There's also going to be a demand on the secondary market for an IS improved PPC. Good for units that had a clan spec ER PPC and can't afford to replace losses. Or for units that had a snubbie, and want more range.
To put your computer examples in context, in those ten years there wasn't a leap in technology like that between SL and Clantech - the architecture between the early 8088 and the 80486 didn't advance that much, and the improvements in performance weren't the same type of advancement we get in Clantech.
Jumping from SL to Clan techbases is more akin to the twenty year gap between the 80286 and the Core series architecture used since 2005 or so.
The changes here didn't result come from use of completely different minerals and elements, so much as how they were used, the tools and processes needed to make them work as they do, along with two decades of advancement in architecture design as well as how chips are built with the inclusion of a lot of the bridges and busses that used to require separate components on the motherboard becoming part of the CPU package itself, as well as the refinement of the equipment and development of new ways to etch circuitry.
Clan Tech assumes that you've not only gotten the right materials, but ask the manufacturing capability to produce it in bulk, with relatively low rates of failure, and that you've also gotten the knowhow to adapt those processes to cope with issues previously unforseen.
While the jump between Clan and IS ERPPC technology from outside the universe looks like 50% more damage, one less ton and one less Critical slot, it's probably more that components which focus the particle beam or which generate them are far more efficient in Clantech (or just smaller so they can pack more into the same package) than IS tech bases can afford to output in large numbers,just because they're not as experienced or efficient due to poorer tools or understanding. And why would you assume it'd be cheaper to make it or buy enhance IS-spec ERPPC, given that it competes with a product that weighs less, isn't as fragile, and does more damage in its own (Clan) technology base, and with a product that more people make and is otherwise identical save for a bit less damage? If you need the gear and knowledge to make Clan ERPPC to make Enhanced IS-spec ERPPC, why Mahe them when I get more value out of going all-in? Why invest in mass production of a product which competes with a better one (Clan spec) or one which has a more competitive market (IS spec)? Why risk it when there's no guarantee of a decent ROI due to it being in that odd position? Especially if it takes resources away from the better product (which I can charge that premium for due to undeniable effectiveness displayed in the invasion)?
So that jump in damage in the enhanced ERPPC? If you can do that, what is the point when it probably depends on the same extra components or refinements in gear and manufacturing that Clantech requires?
Or to go back to the computer examples you dragged out, I could take a i9 back to 1980 with the specs, but while Intel existed then, I can pretty much guarantee that the fabs could not reproduce it as the etching tech we use now just didn't exist then. I'm also not sure if our xray machines had five enough resolutions with the films back then to make it possible to study this this structures were laid down. We'd have to advance the material sciences, chemistry, engineering, and refine the knowledge of how to program for that architecture do it could actually DO things.
Edit - don't type on phones, kids!
