OK, so the the Taiwanese don't want to get ripped off by having them built in the US and there isn't anyone else willing to anger the PRC. In a sense, they are being blackmailed: either they build it in US or don't build it anywhere else, (including in Taiwan-without the blueprints); which will leave them volnurable to PLAN naval blockade!
Well that is and isn't true. Taiwan won't agree to them being built in the US if the price is as high as some estimates say - over $1 billion each. The big issue is if some European firms can be brought on board to help - Spain has come up in articles repeatedly, as it doesn't trade nearly as much with China as Germany does. The problem is I don't know whether these European firms would merely be helping the Americans build them, or whether they would actually be expected to build them directly in Europe. Also I don't know what the position of the Spanish government is, for example - we already know the Germans won't sell them.
Also there has been discussion of some of the work happening in Taiwan - build the first "batch" overseas and then have the rest made in Taiwan with help from the builder. But I don't know whether that would be possible now without making the price unacceptable, despite information gained about building submarines from the 1980s Dutch purchase.
It isn't really blackmail, because the US can't make them that easily. Opening a production line of conventional submarines in the US
just to supply Taiwan with 8 would not be cheap - profit would have to come from the price-tag, rather than securing multiple orders for a greater overall number.
No more submarines would be troublesome for Taiwan, to be sure. Then again its ASW capabilities will be greatly enhanced by the P-3C Orions - maybe the money could be better spent elsewhere.