I think it all depends on how much of your net worth you want going down in value. If you have a higher net worth, it will become a smaller percentage and therefore, can be a bigger amount and not detract from your net worth growth.
Personally, we drove around the $1,000-$3,000 beater vehicles until we had kids. Since then, we’ve saved up and purchased 2 $8,000-$12,000 vehicles. Currently these 2 vehicles are down to being worth about $8,000 combined. Our net worth is over $120,000 currently, so this is about 6.7% (8,000/120,000) of our net worth value. I’m fine with that.
You have to find what you are comfortable with though and what you are looking to accomplish out of this purchase.