Jupyter is clearly an attempt to recreate the Mathematica notebook modality, but open it up to a very wide variety of languages. For some people, particularly who write very short programs, Jupyter will be wonderful, but the notebook idea breaks down badly once you have a program that requires a great deal of vertical scrolling, which causes you to lose context. If you choose to put your program inline with the results, it implies the results are succinct, and the program and the results can coexist peacefully on the screen. Mathematica is a very strong product, and for $320 very reasonably priced considering the hundreds of thousands of man-hours poured into the product. But i wouldn't call it easy to use or learn. As it is based on a symbolic arithmetic model (basically a copy of Macsyma), it is really quite different than other systems, and really lives in its own world, because it really can't connect well to existing operating systems and external things that aren't symbolic. It is its own universe, and quite powerful. Not many people need the vast array of math functions that Mathematica offers, and products that are more like Excel like AirTable are going to run rings around Wolfram's company.