Well, from the initial desire to make the figure to the final product can literally take years. Sometimes I’ll want to make a character, but the means of making it won’t exist yet, or might be too costly at that time. Other times I’ll have a hard time figuring out how to proceed with a project, but months later I’ll have inspiration as to how.
Assuming I have all the materials, the average figure might take a few days to several weeks depending on my interest in the character and interference from real life. As for money, that’s hard to say. As an artist, I keep a large supply of materials on hand at all times. That includes “fodder,” or figures bought with the express purpose of using them in future custom projects. In most instances, I can go to the fodder boxes and pull what I need to start work, without having to purchase anything at that moment.