they’re using hdpe which is pretty expensive and meant for thousands of stencils. You could ask them to cut it out of styrene which will give you a couple of uses… probably lower the price a bit.
We’d probably be at or more though, maybe less if it was a trade partner. You have art setup, approval, setting up the cnc, cutting and popping everything out/ cleaning up the edges, packaging, etc. $200 seems like a lot… but they’re using a 100k machine to do it.
Do you Have a plotter? You can cut .010 or even .020 styrene on one, which will make a stencil that will last quite awhile. Before we had a flatbed cutter I used our graphtec to cut core labels out of .030 styrene… it took 2 passes but it worked. It cuts 99% of the way through then you just pop them out