Every cactus is going to have some degree of natural variability in it's alkaloid content, but in my experience the Big Mac is no more potent per weight than a good torch/bridge/pedro. Now again, I haven't dealt with it in big numbers, but I found it to be nothing above and beyond the other cacti I had used. I feel it is more of a plant for those who grow as it has a unique morphology - the collectors who are into the different varietals like it, but for someone who is just going to chop it up, I would say use the money for a known good strain of pedro or torch. The Big Macs I've seen are more expensive.