Our project is over 13 years old, used on millions of servers, and is about 95% written by one guy. There are some measurable benefits, like translations and more participatory users who help find bugs faster and occasionally even send patches. But, the odds of outside developers joining a non-developer-centric project, without some sort of incentive, are slim. So, developer tools tend to attract a lot of help. End user applications rarely do (look at GNOME for an example; it's the most important piece of desktop Linux, and yet 90% of the code is being written and maintained by people who are employed full-time to work on said code; volunteers make up a tiny portion of the project).
There are other good reasons to develop software under an Open Source model. But developers working for free is not one of them in the majority of cases, and you'll probably spend more time herding cats than actually getting work done, if that were your primary goal.
If you do it simply because you think it's going to save you some work, it won't pay off. Do it because you want other people to benefit from it, but don't expect much from them and maybe it will just happen.
> If you do it simply because you think it's going to save you some work, it won't pay off.
A very immature blanket statement. Sometimes it will pay off, sometimes not. Depends on everything success usually depends on - open source is not some kind of magical exception. If you have a good product, but you feel like you won't be able to support it forever on your own or you don't expect or want to earn money from it anyway, you will open source it. In the end, it always boils down to wanting help with the workload though. If you had infinite time, you would just write everything yourself. I know I would, it's a lot more satisfying and interesting. But since we are all mere mortals with generally empty bellies, we open source secondary pillars of our livelihood. Nothing wrong with it, that's how it is.