Yes, it's true, not every tool will do everything you want. That is true of pretty much all software out there, whether you bought it, wrote it, bought the source code and adapted it, etc.
However I use Event Manager on all of my instances and there is nothing that I have needed to date that it doesn't do.
Also, analyzing SQL Server Error Logs seems to be a bit of a disparate process from being told that a job failed, and I don't know that it is something you should expect from a tool dedicated to monitoring SQL Server Agent. It sounds like something more along the lines of a SQL Server error monitor tool.
As for the $2,000 figure, well, you can certainly get tools like Event Manager for less than $2,000 per instance. And what I hate about these debates is that managers and even some IT folks and DBAs think that their time spent developing software is free. Surely the amount of time you spent writing your code was worth well more than $2,000 in opportunity cost that you could have devoted to other tasks, and so you have not saved any money really, just shifted the line item on the income statement from "3rd party software" to "employee salary." Especially if you end up charging overtime or off-hours compensation because you couldn't get your normal work done while you were re-inventing the wheel. :-)