You would need to be paying your web devs something like $3000-$12000/hour for a 'coming soon' page to cost $1000 to do in-house.
At this point, on my day job, my time is worth $75 an hour. So, if I can save 6 minutes, I've saved myself $7.50. By spending $5 a month on launchsplash, I've saved myself about $250 worth of my time.
It's not a matter of having to use the service. It's a matter of expediency. The quickest/cheapest way to get from point a to point b for me is to outsource my splash page and email collection right now. It's not a core competency, why not outsource it?
But, you have to understand some of the developers I've worked with over the years. No question they would have that much into before the darn thing worked right.