I have had an Euphorbia heptagona for several years and it looks nothing at all like the e-bay plant. Photos of my plant have been posted here in the distant past without any questions regarding its identity. Nearly all the pieces are indeed 7 sided and it has never sprouted leaves like the one in the e-bay photo.
The photo above is of my plant circa 2009. It has since grown considerably - branching out from each of the tips .
“Whenever people say, 'We mustn't be sentimental,' you can take it they are about to do something cruel. And if they add, 'We must be realistic,' they mean they are going to make money out of it.”
― Brigid Brophy
You're so right...the plant in the eBay pic isn't E. heptagona or anything similar, unlike the plant in your pic, which may be.
The eBay plant is one of impossible-to-identify E. abyssinica/E. candelabrum/E. ingens tree species
That listing is offensive for two reasons (1) gross misidentification, and (2) From a reputable seller, grossly overcharging... $106? Home Depot sells the same thing for 29 bucks.
