Fiberoptic cables aren't perfectly straight either, and light in space is about 30% faster than light in fiber. Considering the link up&down to space adds about

Fiberoptic cables aren't perfectly straight either, and light in space is about 30% faster than light in fiber. Considering the link up&down to space adds about 1100km, the break-even point is at around cross-continental distances. The speed difference is big enough that high-frequency traders have been using microwave relay networks for years now. Turns out that a relay chain of point-to-point radio links (which also operate at light-in-space speeds) has enough of an advantage over regular fiber links to be worth the hassle.