An ARE or Leer is $3000, then when you add a decent window about $3400.
Then you have a camper shell, which like everyone else, you will hate and sell cheap in a few years. You can't get to anything, can't stand up, etc.
Do your Dad a favor and point him to a popup or wedge truck camper. 1000% more usefulness, can sleep in there in bed, standup in there, access all the storage...
Like everyone else, I started off looking at an ARE topper, the DCU large commercial. Ended up getting a Tune M1 lol.
Show him this Topo Toppers for a Tundra, $7450.
The Mesa, our high quality, durable, lightweight and spacious wedge style camper shell.
www.topotoppers.com