In my previous ventures that'd be unthinkable, but we've effecticely outsourced the position to Amazon.
We spent years as an industry separating out roles and building walled gardens. The latter was bad but the former was correctly informed.
Certainly the "tending hardware" part of sysadminry is outsourceable, but unless you're going full-serverless there's still a bunch of systems work to do - so it may be longer before a full time sysadmin is worth the money, but one will likely be value for money eventually.
With immutable infrastructure all defined in config file (cloudformation, terraform, etc), you don't have any pet servers sitting around.