AppointmentReminder.com wanted $30k. AppointmentReminder.org was available for $8.95. You'll note that I'm still #1 on Google due to the exact match bonus, so mission accomplished plus $29,991.05 in my pocket. This is still an attractive option if you're doing something where brandability isn't all that important.
If you're going for something a bit more brandable, there are plenty of domains in the sub-$2k range which are at least as good as, say, Dropbox, Kabbage, Snapchat, etc etc, and probably many more which are not obviously attractive names but won't hurt your company at all (Twilio, Airbnb, etc).
There's also a virtually infinite number of NAMEapp, getNAME, NAMEnow, etc etc available on any TLD you care to name available for the registration fee. Many startups start that way.