DO - you must go from distro and pay, to run meteor app from 10 users.
I still think DO is the cheapest option on this list, although it does require some setup. However you can get much more power and processing capability then you would get on Galaxy for a fraction of the cost. Zodern's continuation of the mup repo on GitHub  is a great tool for automating this.
If you have sysadmin knowledge, you can also host your own mongo cluster there for very cheap, but that's more complex then just setting up the app.
Also when it comes to uptime and SLAs on galaxy, I think there is cause for some concern . Perhaps this has changed in the past months but I wouldn't be able to speak to that