People definitely do expect a higher level of support when they pay for things. It's just like with the cheap clones vs. genuine boards. If I buy some Nanos on Aliexpress for $1.95/each with free shipping and one of them doesn't work I'll probably just chalk that up to an acceptable loss rate and decide it's not worth hassling the seller over. If I buy official Nanos for $22 + shipping and handling I'm definitely going to expect Arduino's customer support to make good if there are any issues and be very disappointed if they don't. The same would hold true with pay software. I tend to not place much value on the level of tech support for a product I'm considering buying because I'm the type who will almost always deal with problems myself rather than waiting on hold to talk to someone who knows less than me.
Charging for support is actually one way people are able to make money on open source software. I'm not sure if there is much of a market for that with the Arduino IDE. The only place I could see that working is for a school that is going to use it in their curriculum.