Around here I think a neuter is around $200. I don't remember was I paid for Korr, but that was over 5 years ago now. I do have 2 intact bucks that will need to be done soon enough, so will have to find out the cost.
2 separate rabbits are really twice the work and expense. You have 2 cages, litter boxes, food and water dishes as well as having to deal with separate run times and play times. Since you have 2 cages and litter boxes, that is twice the litter/bedding. Hay and pellets are also twice as much, but this can vary depending on the rabbits. Vet bill are also for 2 rabbits, but some vets may give a small discount if you bring in 2 at once.
2 bonded rabbits aren't as much as 1. You should have a bigger cage, so that can be a bit more work as well as more bedding to cover it. As far as litter, it is less than 2 separate ones, but a bit more than a single. Food is about twice a much since they do eat the same as they would if each was single. You only have to do one run time.
A bonded pair is not that much more work than a single rabbit, but does cost more. 2 single rabbits are more work and more cost.