The problem occurs due to timing issues. At the time when change event handler is executed, the editable cell is already closed and associated HTML elements are not part of the DOM tree anymore.
I can suggest you another similar approach which I believe will fit in your needs. Instead of to the change event you may hook up to the select event. Also instead of set method, you should use the standard "=" operator to change the values.
grid = $(
model = grid.dataItem(
model.UnitPrice = 100;
For your convenience I updated previous sample:
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