I often come across bogus patents when i come up with small business ideas, but the cost for reexamination is so high as to bar entry into some domains (from $1

I often come across bogus patents when i come up with small business ideas, but the cost for reexamination is so high as to bar entry into some domains (from $13000). Why are the costs so high to point out a mistake in the decision to grant a patent? Is the reexamination fee reimbursed should the patent be found invalid?