One customer running a single WordPress was using a 4x vCPUs instance on Amazon AWS®. 但是 CPU 和负载使用率非常高, 没有明显的理由 (参观人数合理). 然而: 每个 404 引发了巨大的CPU和带宽消耗! 进行了测试，并且 404 was replaced by a flat and tiny 324 bytes HTML file. The result: the instance size could be divided by two, so halving all expenses (including the bandwidth).
When using a custom 404-page: one should not forget that even a simple dead link to an image will trigger an expensive and huge HTML code being returned to the browser, resulting in sluggish speeds for the visitors as well!
换句话说: do not do it, even if it looks pretty to the eyes.