Cartridge - sweet spot on the cost/sound curve?

Everyone has their preferences.  As mulveling points out aluminum cantilevers can sound very good.  Personally, I tend to prefer them over other exotics such as boron or beryllium.  This is a personal taste thing, there is no right or wrong, just a matter of taste.  In your price range in addition to Audio Technica, excellent BTW, consider Ortofon, perhaps a 2M Bronze.  This assumes you determine that you do need a new cartridge after following Elliott's suggestions.

I have Goldring 1042 MM for my Nottingham Spacedeck/Spacearm. Bought it years ago from analogueseduction.net in the UK for $350. Now it is probably more, US prices are $600 or so. I doubt you will find an overall better cartridge in this price range. It does nothing wrong and many things right or I would've replaced it long ago.

I would get an Audio Technica VM540 MM cartridge.  It sounds fantastic and comes in around $280.00.  You will not be disappointed and I think sounds better than the Blue Point Soecial.  I owned one mounted on a Rega Planer3 turntable.   I found it thin and bright.  You could look into the Grado cartridges.  They have a moving iron cartridge for around $300.00.  

Grado at this level may give you a foggy unbalanced sound.

The Needleclinic NC-103 is less than $600 and it blows aways cartridges costing multiples of its price.

https://trackingangle.com/equipment/needle-clinics-denon-103-phono-cartridge