They vary so much. You can get them at Lowes, Menards, etc, for like $15-30. Or you can go to a tree farm, take the tractor out to the field, and cut one down yourself (they have pre-cut too) for like $100+. At least this was my experience at a tree farm in Noblesville. Other farms may vary.
Warning
No formatter is installed for the format bbhtml
Re: How much do real trees cost?
We usually go to Dull's tree farm and typically spend around $25-40 for a 7'-ish tree.
ETA: https://dullstreefarm.com/faqs.php