They could perhaps bid but intentionally not win much. I think the harder part would be to represent themselves as a legitimate buyer, with some level of spend

They could perhaps bid but intentionally not win much. I think the harder part would be to represent themselves as a legitimate buyer, with some level of spend, which probably wouldn't be too difficult either, but it's a question of value I suppose: if they have customers with deep pockets, no big deal. The platform I work on aggregates about 3-4M qps so getting 700K qps is certainly feasible. I suspect this type of thing is more common than people realize but I have no evidence to support the suspicion.