I don't know anyone mass buying V100s; it is just the example used to solve #120 because that is the type and number of cards that were used to solve #110 and #115.
I feel like #120 is going to be solved by large numbers of older cards lying around in people's garages somewhere, rather than with anything that can be rented with AWS or Vast. Even a 100 of any high-end cards just seems too expensive for someone with deep pockets to rent in the long run and you can get better results searching with a few thousand of people's Maxwell and Pascal cards (and even Radeons if Kangaroo ever gets ported to OpenCL).