Thanks for all the responses.
I should clarify that I am donating the thread (and some other supplies), so I am just looking for a place to buy it inexpensively in bulk. My sister takes quilting classes at this non-profit and I am friends with the teacher, so when she runs out of supplies and money towards the end of the fiscal year for the school, she gives me a list of things she needs. Although I am within driving distance, the non-profit is in another state so I usually just give the things to my sister when I visit and she carries them in when she goes to class.
I went to the Marshalls Dry Goods website but couldn't find any thread there. So far Connecting Threads looks like the best deal for regular size spools. Since the teacher supervises quite a few students in the classroom, I assume she wants regular thread spools; however, I'll ask her if she could use cones instead as they seem to be quite a bit less expensive.