Laying tile is about a 6 on a difficulty scale from 1 to 10. Tile and grout are waterproof, so as long as you have good mastic holding your tile in place and do a decent job of grouting the tile, you don't have to worry about leakage. Grouting the tile is about a 2 level of difficulty. It's not hard to get it right. It's just a time consuming job.

The cost of materials, like any home construction project, will vary depending on the quality of finish. I'd guess maybe $1500-$3000 for materials. It's probably an 8-10 hour job. $24,000 is an insane number