I wouldn't call ASML's products complimentary. They are the only machines capable of EUV lithography. Without EUV, nodes smaller than 7nm wouldn't be possible. But even before EUV they were the leading manufacturer of lithography machines. They deliver to all the big players like TSMC, Samsung and Intel.
They are so important/valuable that the US government is negotiating with the Dutch government to ban ASML from selling EUV machines to China.
I remember bridgewater shorted ASML for big positions for no reason and then the news broke out that US government banned ASML from selling some stuff to China.
Now I think their product lines complement each other nicely on a fab floor.