I was studying Miller-Modigliani theorem and one of the stated assumptions was that there will be no bankruptcy cost to the firms.
Does the assumption of "no bankruptcy cost" assume that in MM world, no company would go bankrupt or is it that the firms can go bankrupt but they may not face direct (such as legal services cost) and indirect costs (loss of operating income due to customers' belief that the firm would go bankrupt)?
If it is the former case, then in MM world(without taxes), why does the cost of debt increase with the leverage? If bondholders are certain that the company won't default, why should they ask for more even when the company keeps on increasing the leverage?
Regards