I may be wrong (as much as the article writers), but I don't even believe any TL 15 shipyard would build a TL 9 ship. Building it with stats that could be reached at TL9, sure, but a true Tl 9, why should they?
A TL9 ship needs trice as larga a PP (at the same price per ton) than a TL15 one, so reducing its payload and costing the triple on it. In MT (the only version I know to enter on those details) it cannot have even artificial gravity (with the ill effects this can have for the crew and passengers health), not thrusters, relying on HEPlar MDs. Only the JD does not vary (aside from having a maximum of J1 capacity)...
As I said, this article depicted (in MT terms) some of the mostusual ships as built in TL9, the results, compared with those in IE (TL15) were:
- Scout (in IE J2, MCr 29) was J1 and costed MCr 53.5)
- Yacht: (in IE (the J4 capacity was an errata, it was J1), 43.6 MCr) costed MCr 49
- Fat Trader (IE MCr 67.5) costed MCr 90.5
- Free trader: (IE MCr 37) costed MCr 52.3
Others, like the Scout, had their JD reduced to 1 (the maximum at TL9) aside from the increased price.
As the article says, it's an inferior product at higher price. So, again, why should a higher TL yard build it?
Sure those shipyards have their building capacity filled with higher TL (and more profitable) commands, and building suchantiques would not be profitable, so they would only be built in TL9 worlds, and few of those have an A starpost to build them (and while HGsays the planetary fleet may build them even with lowerstarport, I guess commercial shipping is not). And even then, no TL price would be obtained, as it would be state of the art for them.
And that's for commercial shipping. If you intend military ships, with better computers (unavailable at TL 9), armor and weaponry, things would probably be worse and price difference increase...