Teachers? Whats the deal with spending?

I hear all the time about HOW MUCH teachers have to purchase out-of-pocket for their classrooms. My FSIL teaches in Plainview in an Excellent SD and her budget is only $100 for the year !!!
Sometimes I hate to see Teachers and Police Officers get so little respect
How much do you really have to spend/are you responsible for in your classroom?

I want to have the best for my students and make my classroom the best that I can, but is this going to be like having another few children?

My Professors have also advised us time and time again, to ask parents for stuff. My Prof owns a private school and she sends letters home in the beginning of every year, and has many parents who give stuff from their profession, whether its paper (Xerox employee) or a skill, or even things like wipes, construction paper, etc etc... She said that parents love to help out for their kids, and love to participate.

What is 'acceptable' to ask of parents?
Another teacher I know is collecting books for her classroom library. Are you responsible for this too ?
Whats a typical year of your spending for your classroom? (voluntary vs obligated?)

Im sure this answer can vary from district to district.

Thanks for any input !

I'm not a teacher, however my son started kindergarden this year and his teacher sent a list home with him of what supplies should be brought in - for the whole class - not just him. From my understanding, this is common, most teachers do this and it is perfectly acceptable.
I thought it was crazy at first but now I totally understand why.

eta: the list went from pencils all the way down to tissues. Everything you could think of was on that list.

My first year I was given a lot of money and I still spent like 700!
Last two years I have spent 200-300 at least. It is so expensive! Every year you need new things!