Invading Taiwan will never be an economically rational action. If it happens, it will be because of internal politics, personal/national myth-making etc.
Taiwan is ridiculously favourable terrain for the defenders; if they fight back, there can't be quick victory, and the US will be able to play merry hell with China's naval logistics from day 1 (obviously with escalating levels of firepower available over time as more resources move in-theatre).
China could secure a more reliable victory by expending most of it's ballistic missile inventory to incapacitate the US bases in Guam and Okinawa, but that would inexorably trigger WWIII.
Taiwan is ridiculously favourable terrain for the defenders; if they fight back, there can't be quick victory, and the US will be able to play merry hell with China's naval logistics from day 1 (obviously with escalating levels of firepower available over time as more resources move in-theatre).
China could secure a more reliable victory by expending most of it's ballistic missile inventory to incapacitate the US bases in Guam and Okinawa, but that would inexorably trigger WWIII.