Well, the question is - does that app have the potential to outgrow the SaaS offerings?
There's plenty of things that won't, for a long time, so you're fine to save the time since you won't need to re-do it later.
But if you can really see the product expanding to a large scale, you need to think a year or more into the future when planning your infrastructure.
The situation I'm in is our apps currently do low enough traffic to exist in a PaaS, but they weren't built that way from the ground up and live on bare metal currently. Migrating to say, AWS, would using ElasticBeanstalk be burdening myself with technical debt I don't currently have vs using something like CloudFormation (Terraform) and CodeDeploy?