I guess some folks love it, but for me, it is just frustrating somehow. I would much rather prefer a fixed price. Does anyone know what the norm are here?

around $1.5 in change, at least for me. Takes way too long to drag over any more than that.  

(Don't know about an upper limit, but you rarely want to go below $5 with these types of things to avoid flat fees potentially eating most of it.)

When we mark an asset free - itch.io automatically prints next to it "Name your own price." 

You don't have to feel guilty about taking the asset for free - it is free. The fixed price is $0.

Otherwise, go with $2 as a minimum. The creator will get about $1 after fees.

Developers can put a default price on “Name your own price”. If you are unsure of what to pay, you can select that amount.

This method can allow a project to be reached by a big number of people, but also get some funding from those who can afford it.