[dralley]

Because they're not a monopoly based on anticompetitive practices, they're a monopoly because what they do is so difficult and massively expensive that the monopoly is the only thing that makes it economically viable. The worldwide market for these machines is only perhaps a few dozen a year at most, it just can't support paying the R&D bills of multiple competitors.

ASML is also part-owned by their customers. Intel, Samsung and TSMC all invested in ASML to get EUV tech over the line - see aforementioned capital requirements.

[pbmonster]

Also, it's only really a monopoly at the top end, and only right now. It's not like ASML is the only company building litho machines. Canon and Nikon still sell a lot of machines, they just decided not invest to much into competing at the top end over the last 10 years.

This could, theoretically, change at any moment, and Canon is trying something with their new generation of nano-print tech.