Yep, I was on vacation and wrote most of the app in a weekend. I wrote the FAQ and about pages on my phone while we were traveling, and then it took one more evening to add most of the products. And I've spent a few more hours fixing bugs and adding some more products. I have to admit, I was surprised at how fast I got it done. It was a really focussed sprint.
Rails app / Reddit integration - I've been a Rails developer for a while, so was very familiar with most of the gems I used. (devise, omniauth, resque, etc.)
Server stuff - Heroku is pricy, but it's awesome. Although I might migrate to a much cheaper Digital Ocean box this weekend.
CSS - Zurb Foundation is amazing. The menu bar, in particular, has really awesome built-in responsiveness. There's a little custom CSS, but most is stock framework.
Admin interface - I used RailsAdmin, which is perfect for small apps. It can do so much out of the box. (For bigger apps, I prefer ActiveAdmin)
Error handling - I just added the airbrake gem and configured my self-hosted Errbit instance. I've had it running on Heroku for a few years now.
QA - Thanks for your help!
The most time-consuming things were writing a simple Reddit API with httparty (none of the gems I looked at supported OAuth), adding very basic PG array support to Rails Admin, and making the site work on mobile (responsive design was very fun to learn).