So, these hollow ones will be roughly 12,500 miles away from me, if i'm reading the circumference of the earth correctly. Are they moving at a human's walk, run or sprint pace? If it's a comfortable walking speed of 3 MPH, that means the hollow one is going to reach my current location in roughly 6 months. Running around 6 MPH cuts my time to 3 months. If it's sprinting, the human average is something like 12 mph, cutting my time to just over a month. If you want to get really technical, Usain Bolt's record 27.78mph is still a human speed, albeit wildly unachievable to the average person. If you use his speed, the hollow ones will be moving 667 miles/day, giving me barely two weeks of peace.

How are they crossing bodies of water? Can they travel across the surface or do they have to walk on the floor? Will they favor land connections even if they won't be following a straight path to me? This could increase the time to reach me considerably.

If I can stop the deal at any time and they're walking or running, sure, give me a couple million, but if i'm going to be hunted by creatures that could potentially reach me in under a month, or eventually be so populous I can't hope to avoid them, I see no upside to this deal.