Is there usually a dramatic difference between $5k and $10k cartridges ?

Yes, but you need a considerable investment in playback equipment to realize the ∆.

I auditioned a Koetsu Jade platinum on a Technics SL1000R using my <$4500 Odyssey electronics and Harbeth P3s. It sounded pretty damn good (noticeably better than my Hana SL/Technics SL1200 GR). When the dealer switched to a BAT Rex II phono pre it sounded strikingly better! (Note: I couldn't afford any of that; the dealer was an old college buddy who was just happy to visit).

I think the 10% rule applies here (cartridge should cost no more than 10% of your system cost). You can spend more, and yes, it will sound better, but you will not be realizing its full potential.

@dogberry Of course you are right. My 10% statement was just meant as a general guideline for someone new to the hobby.

For a person trying to thoughtfully put a system together, getting a decent cartridge that is a good match with your system (or the one you want to buy) can be tricky. Typically that knowledge comes later in the journey. My best advice for a serious
beginner is to work with a trusted dealer.

Note: 10% would be near the top end. There a plenty of great sounding carts that cost significantly less than that. Two of my favorites are my Nagaoka MP 110 and  Grado Gold3. Both of those carts are a hoot and will sound great in any system!