Our UR5e carton-insert proposal prices the arm and gripper but leaves the mounting-kit presentation fixture as 'by others'. I am gathering the missing guarding and training costs too. But I cannot compare two totals when one supplier expects us to design the fixture and the other includes it.
I got caught by a bundle description that sounded much more complete than it was. For yours, I would put the fixture work in its own row and ask both suppliers who designs, makes and tries it with your actual kit. You may still choose to supply it yourself. At least then it is a choice with work attached, rather than a mysteriously cheaper quote.
That split helped. The cheaper proposal includes neither design nor manufacture. Our toolroom can price manufacture, but has not accepted design responsibility. I have left that cost blank instead of treating our toolroom as free scope.