Bad performance with TransitionMotion and large lists.

I'm facing very bad performance when using TransiotionMotion with medium sized lists (~ 50-100). When a new item is inserted to the list, after it's rendered and has about 100 items, the animation is super slow (Chrome-Desktop).

Works fine with smaller lists.
Here's my code: [https://gist.github.com/itaydressler/9d624de8bcee1798750aa24ad24035e2](url).

Start by reproducing the issue with the linked gist in Chrome using a 50–100 item list and profile the TransitionMotion update and animation. Compare insertion performance with smaller lists; done requires identifying the cause of the slowdown and confirming improved performance with a comparable large-list case.

Written by the indexing model from the issue text.