Unfortunately the 7980XE does not appear to be available for purchase yet :(
Intel's site says Q3 (which ends this month): https://ark.intel.com/products/126699/Intel-Core-i9-7980XE-X...
And in a blog post they appeared to indicate the 7980XE would be available Sept 25 (at least the 14-core version, which also hasn't yet appeared, depending on parsing): https://newsroom.intel.com/news/intel-unveils-full-intel-cor...