Unless they want the unit pricing for future work ie. You did the last job of changing out 1000 lamps @ $10 per for 10K. I have 3 lamps I need changed out here's your $30. It doesn't work that way. If there's a known amount of lamps to change out it's fine because you'll build everything in to the overall price.Every bid is counting installed items or assemblies.
It doesn't matter to me how the number is presented to the client, it's going to be a number no matter what so, go ahead and divide the final price into installed units.
Changing 1000 lamps.
$10 per lamp.