You can get Office Student and Teacher's Edition for about US $110-125,
which is about the cheapest retail Office version around. You must have a
student or teacher in your household, however, or be in some way connected
to education.
eBay has Outlook or Office available for less, but generally it will be
someone else's old copy and you must be careful that it's not someone's OEM
license being sold because that's not permitted under an OEM EULA.