What's the difference between the 50-80$ Egyptian 100% cotton mattress encasements on Amazon, and the 170-300$ 100% cotton encasements at specialized mattress sites?

[looking4mattress]

In my previous post, I found a few different mattress encasements, there are a few 100% cotton encasements that range from 170-300.

Where to buy cotton and/or bamboo/tencel mattress encasements that are 13 inches?

I’m looking for a knit cotton and/or bamboo/tencel mattress encasement for my mattress. It has an 8 inch coil base if that makes a difference, and 5 inches of talalay latex, and some wool batting wraps for the latex for fire resistance. I am in a hot area and I love bamboo for it’s temp properties, so would prefer if that’s available. But maybe bamboo for the whole encasement may not be necessary, as it probably only counts on the sleeping surface, might be more prudent just to get bamboo sheet…

But I was checking on Amazon, and they seem to have a bunch ranging from 50-80. They all say ‘100% Egyptian cotton’.

What’s the difference between these two sets of encasements? Is Egyptian cotton cheap or something?

Edit, if it makes a difference, I was looking at 14-16 inch deep full sized.