It's true, a 'custom' bamboo rod is likely well beyond most people's budget. It's also true you can get a less expensive bamboo rod. likely a production one (Montague, Horrocks-Ibbotson, Goodwin Granger, etc. amongst others). For example, look on E-Bay. But realize the taper of the bamboo rod makes all the difference in the world as to how it casts and feels in the hand. Two bamboo rods of the same length and weight may have different actions depending on the taper. People also complain some of the older bamboo rods were heavy and it's true in comparison to graphite rods. It's a fiction to say a graphite rod is going to imitate the action of a bamboo rod. Which bamboo rod? Besides, put aside the cost of the bamboo rods for a second. Which one do you like better when casting it? It could be the less expensive bamboo rod. What you like to cast is really the bottom line.
As much as I dislike Sage rods because they're too fast for me, graphite has its advantages. You have to be more patient with your casting stroke on a bamboo rod than a graphite rod. Moreover, if you break a graphite rod then it is not that big of a deal. Break a bamboo rod and you may need to have a bamboo rod maker rebuild the broken section if you want to keep the taper. They might be able to repair it if the break isn't too bad. Matching the color of the replacement section and wraps on an older bamboo rod may not be possible. Graphite on the other hand just requires you to slap in a replacement section and it'll probably look like the original section. Besides, break an expensive custom bamboo rod and you'll probably feel a range of emotions (self-loathing, resignation, queasy, angry and at the very least, stupid) unlike breaking a graphite rod. Moreover, playing and reeling in a fish on a bamboo rod is entirely different than on a graphite rod. You've got to be aware and careful.
One thing is for sure, a custom bamboo rod will always be an heirloom. A less expensive production bamboo rod and graphite rod won't. You likely wouldn't put a graphite rod above the mantle. But a rod is ultimately just a tool to catch a fish with.
Still, I really can't see buying graphite to imitate the feel of a good bamboo rod. Who knows though? I'd have to cast the Sage Circa rod to make that assessment.