The tool is there to ensure proper clocking of the cams relative to each other and the crank. It speeds up installation and ensures the cams are timed correctly.
If there are witness marks on the cams to indicate positioning I'd wager you could do a topend without that tool. If there are no marks than the tool is practically a must just depends how they engineered it for install and repair.
Also I doubt o.e.m.s make tools to garner a profit. It's extensive r&d and cost and how many people are going to buy them. BMW for instance has more tools than they do production cars, no way in hell are they making money off of tool sales, if anything they're losing it since really only dealers have them.