We have a BabyLock dealer that sells the BL9 for $99, too if you purchase several(4) maybe inquire about a discount. Never hurts to ask.
I agree working with alike machines would make things easier for you and the students. JMHO.
I think Hancock's sometime around Thanksgiving-Christmas puts Janome Machines on sale.
Too, I purchased my Singer 15-91 for $80, I have noticed the asking prices are rising.
Good luck in your endeavors, let us know what you decide and how it all shakes out.