The runway is going to be your time and attention span, not $10/mo.

I don't know what you value your time or opportunity cost as... but the $10/mo doesn't need to save very many minutes of your time deferring dealing with a resource constraint or add too much reliability to pay off.

If resource limitations end up upsetting one end user, that costs more than $10.

This assumes you have to spend any time or attention worrying. 1GB is plenty of memory for backend type stuff.

And most VPSs allow increasing memory with a click of a button and a reboot.