Those numbers seem a bit off.
Last time I saw the numbers were 2.4b for 100 HCDS launchers and 400 Harpoons.
I think this is the right kind of system to buy in terms of a defense perspective. However, I think as people mentioned, PLA has already developed the counter. J-16 covered by J-16D EW as well as Y-8EW to conduct SEAD and then take out these targets. Any surprise Y-8 recon types are the most commonly flown aircraft?
PAVE PAWs is very powerful, but the issue is being a fixed target makes it totally vulnerable to BM attack. If you move HAWK and Patriot batteries to protect it, then that leaves the AShM launchers vulnerable to aircraft attack. Avenger Stingers are useless against J-16.
I think the greatest hinderance to the military on Taiwan is money. There are so many aspects of defense to cover, and the reality is that you can't say "only invest in the air force" or "only invest in the navy", when the reality is that any modern conflict is a combined arms affair. Canada has many times the landmass and about equal population to Taiwan, but only an active air force half the size.
With this in mind, I think they should prioritize self-developed systems.
1. The obvious self-sufficiency angle
2. Minimize cost for buying US equipment
US Defense contractors are public companies, they are not helping you for free. Either make the US government pay for the equipment (like Israel does), or get the cheapest price possible