Worth the wait, worth the money.
I'll try my best to give a spoiler free review.
I'd like to ask those people who are saying this movie wasn't good or well written or didn't have a storyline etc. It was a BRILLIANT movie, with a satisfying conclusion for the Lambert family. With a few shocks too.
The flashbacks were the best and enough to give you goosebumps; callbacks to the first two movies Insidious and Insidious 2, with scenes, flashbacks and backstories of other older characters; both the protagonists and antagonists. Needless to say, the movie was extremely nostalgic too which made it even more relatable and enjoyable.
The best part is that this movie doesn't rule out the possibility of a sixth movie either, so that's something to cheer about as well.
Insidious 5 (Insidious: The red door) is a perfect ending to a very nice trilogy featuring the Lambert family.