I did not tile the cage for several reasons. First and most importantly it would have made the cage heavier, secondly, grout gets dirty quick and another important reason is that it would easily crack over time. Floors are screwed down a lot so that they do not move in a house. All this is is a sheet of 5/8 plywood that has some flex, I don't see tile ever working unless the cage is built into a wall and will never move.
How do I fill in the screw holes? With what?
As for cost, it is what it is, I do not know how to bring it down, this is just the way I do things.