Put another way, if my library dropped Kanopy, almost no one would notice. So it's hard to claim Kanopy is being "predatory" as another commenter mentioned.
I get that the infrastructure for streaming isn't cheap, and neither are the licensing fees, but this feels like price gouging. I know price gouging is a specific legal term but I'm speaking in the vernacular sense.
I also understand that my library has a lot more data to make the decision than my feeling of guilt. There's no need to speculate. Email your library and ask them:
"Would you prefer I stream title X from Kanopy, or check out the DVD?"
And also ask
"Would you prefer I stream title Y from Kanopy, for which you don't carry the DVD?"
Feel free to provide the context, expressing concerns that it'll potentially cost them over $150, and you're worried that they are being abused by Kanopy.
If the library's not willing to tell me to prefer the DVD, then I'm not concerned.