Hope this isn't a respost, but I was on Amazon.ca picking up the DOTD and happened across this little gem: Ghostbusters for Xbox 360 for $30.14 (weird amount). So far, this is the cheapest I've seen it.
http://www.amazon.ca/exec/obidos/ASIN/B000ZKBJXC/ref=pd_luc_mri?_encoding=UTF8&m=A3DWYIK6Y9EEQB