I've found the opposite to be true. There's lots of mid-level developers around who are capable of handling most common stacks. Even mid-level Ops people are few and far between. Truly senior Ops people are a rarity and in very high demand, even if salaries aren't matched to that demand. The difference in responsibility in those roles that you are entrusting an employee with makes the comparison a bit difficult, but generally speaking far more is expected of Ops hires than Developer hires at most companies. When you hold the keys to the kingdom you have an extraordinary ability to cause damage to the company purely through innocent mistakes, much less malicious behavior.