Kangaroo isn’t that expensive. I bought 6 large strips of kangaroo tail leather from the fellow on ebay – it worked out to about $10 each with shipping. Some had more creases and blemishes than others, so finding a ‘perfect’ piece could drive the cost up.
The fibers in kangaroo leather are no finer than in other leathers, but they are more interwoven. I believe this is why the leather is so tough and pliable. On a paddle strop it is nearly as firm as wood. Anecdotally, I have had some outstanding results with 0.25 diamond on a kangaroo paddle strop. A well prepared strip of cow hide (actually processed into a strop) is likely just as effective and likely costs about the same.
I have not personally used the WE leather strops, so I don’t know how compressible they are.