Why do D&D books have to be so expensive?

I just wanna start DMing a game and I need to buy $150 in books to do so? The fuck.

Edit: Lots of people telling me to play other systems. Here’s what’s up:

• I want to play a 1-on-1 game with my wife
• I’ve never DMed before
• She’s never played a TTRPG, so this would be her introduction
• She’s been reading a lot of fae-related fantasy, which has me thinking she may want to play roleplay heavy with some fae storylines present
• Ideally the system wouldn’t be too crunchy or combat focused

Edit 2: I’ve spoken with her and she actually wants a more modern setting