Even in a droid-heavy universe, you might also consider the time it takes to make back their cost as a factor in both the target end price and when a sophont would be a more logical choice. We do have numbers for how much it costs to hire a sophont, so that will be the economic breakpoint. A hired Engineer should be at least Engineering 1 in Jump Drives. With characteristics bonuses and expert software and toolkits etc. they should be operating at Engineering 2-3 in their specialist field and 1-2 in all others.
Robots don't need staterooms or life support (and the power is effectively free) so you can take that into account also. They do however require annual maintenance and whilst that cost isn't great (0.1%) for the more expensive droids it starts to become a factor.
We are probably not talking about the "life" of a droid since they can be eternal if they have regular annual maintenance but more the economic life for each owner.
A flesh-bag Engineer costs you Cr4000 per month, shared stateroom is another Cr1000, plus it also represents 2DTons of cargo you can't carry so on average Cr2000 in opportunity cost. Overall you are looking at saving Cr7000 per month or KCr84 per year. That makes the basic models a no-brainer (assuming you have the capital up front) as it pays for itself in just over a year, especially as it gives you a crew member who can work if life support fails and is likely expendable if there is a radiation leak or fire etc. Depending on YTU standard or hired Engineer it maybe a little less skilled, but not all hired engineers are that good in all areas.
The advanced one pays for itself in around two and a half years and is on-par with even good hired on Engineers and if you buy it on finance (i.e. as part of the ship) then it is a sound investment.
The supervisor is more of a challenge and this is where I think the Sophont becomes more likely. Whilst skill level 5 is impressive, it is seldom required. Higher skilled sophonts can command a higher salary (and probably their own stateroom) but it probably won't make their monthly cost much higher than KCr10. At that pay It will take 18 years for the supervisor droid to pay for itself (taking the maintenance costs into account). That is far less easy to justify. In 18 years it is easy to anticipate there will be some sort of breakdown in an expensive component or total loss. While this would be a tragedy for a flesh-bag hireling, to be hard-nosed, you won't have to pay for a replacement, you just hire on a new crewman.
So my take would be that once you need a Formidable Task capability, a skilled sophont crewman is probably the better option. In less droid-heavy universes (or heavily unionised ones) the threshold might be Very Difficult Tasks.