A lot of people are saying that Heroku is expensive. While it's true that the monthly costs will be higher for Heroku than AWS, I don't think many people are looking at the true cost to the business.
Heroku requires very little setup whereas the same cannot be said for AWS. If an engineer spends 2 hours setting up AWS (still relatively little time), and you pay that engineer $80/hr, then AWS better save you $140 assuming the same engineer would spend 15 minutes ($20) setting up Heroku.
As of this moment, a hobby dyno on Heroku costs $7/month. If you needed to support more than a few dozen concurrent users (which it sounds like you don't), you would need a 1x dyno, which is $25/month. This means your ROI for deploying to AWS would be $140 / ($7 / month) = 20 months.
Of course this calculation depends upon cost of engineering time and quality (speed) of engineers as well as the scale of the application, but it sounds like in your case Heroku will be cheaper.