Money has absolutely nothing to do with it, what can your local general practioner do for you to increase the size of your penis and profit from it? Nothing. So why would they care if you tried to do it yourself? Are they married to a penis pill millionaire? Do they play golf with surgical penis enlargers? Probably not. But they are still going to tell you not to do it, and that it won't work anyway. Why? Three main reasons off the top of my head:
1. Most Doctors would be more concerned with the psychological reasons behind your desire for a bigger penis, than any physical issues regarding intercourse, and are prone to regard most penii (excluding the condition known as micropenis) to be "normal". They may also go on to remind you that the majority of nerve endings in the vagina are in the first three inches.
2. A qualified Doctor has spent years studying the human anatomy in great detail and yes it is sad but true that once they have been indoctrinated in a specific unshakable way of understanding the human body, they are reluctant to question this knowledge. If they were taught in medical school that the penis is a delicate instrument that will not grow after puberty, they will hang on to that concept with all the viguer of a fag hating christian right-winger.
3. The possibility of injuring yourself. "Why take the risk?" would be the likely line here. You have to remember these people deal with sick and dying people, the terminally ill, horrific accidents and diseases like cancer. When they juxtapose the idea of penis enlargement with these grim realities, they tend to see one as quite frivolous and not worthy of investigation or resources.
