I priced an arm and gripper for spacer unloading, then told my colleague the fixture was only a little job; he asked how little and I had nothing, so what should our first pilot estimate actually contain?
Ask whoever makes the fixture to estimate the work, including changes after the first trial, because little is currently standing in for somebody else's time.
Before any fixture gets made, time the manual unload and watch where the fiddly bits are. We had a proposed handling exercise where getting the parts into a sensible starting position took longer than moving them. Lovely robot problem, poor reason to buy a robot.
Include the people needed for the trial too, not just the machining estimate; someone will prepare parts, supervise it and deal with the interruptions.
When I get called back to a supposedly simple job, it's usually an awkward part or a recovery nobody taught. Budget a second person learning those cases, not just you becoming very good at rescuing the pilot.