If you're willing to spend $5/mo then DigitalOcean is a safe bet with excellent reliability. If you're a new customer then google for a Coupon before you sign up (saves you $20).
Don't try to go even cheaper, that way lies madness.
You cant compare AppEngine with DO or Heroku with AWS.
Yes, AppEngine is costlier than DO 5-10X is comparing cost of computation power. You pay the price for not having to deal with DevOps, scalability and some cool API/services.
Don't try to go even cheaper, that way lies madness.