I own a maschine plus and upgraded to Komplete 13 standard a few years ago.
Just had a look at updating to Komplete 15 standard and it says I have to do the more expensive upgrade to Komplete 15. The price difference is update is 179pounds v upgrade 449pounds.
I'm not at all impressed with this and to be honest, I'm not surprised.
NI is just a money making venture now and don't care about their old customers.
(...now resolved.....)