I don't know if confluence will install on shared hosting or not, but don't forget mediawiki definitely will install in shared hosting. If you don't have other atlassian packages why is it important to use confluence as opposed to another wiki?
I am a huge fan of the entire atlassian suite. Unfortunately in recent years the pricing has been restructured to the point that it makes no sense to any organization except the largest of organizations. Sure the pricing page makes it look very enticing to the under 10 user organization, but the numbers for the entire suite are really hard to crunch when you reach the 11th user.