When you're deploying a small army of lawyers, investment bankers and accountants, the costs tend to add up really quickly. To respond to your specific question about the cost of the IPO in proportion to its size: there is a floor on how expensive a traditional IPO will be when all IPOs have a certain minimum amount of due diligence required. Even if the IPO itself is not remarkably large, there is something of an "activation level" that you'll pay just to initiate the process and get everything moving.