Cartridge - sweet spot on the cost/sound curve?

I meant to say, when buying new, I prefer lighter/stiffer boron for cantilever material over aluminum

If your phono stage can handle low output moving coil cartridges a Denon DL 310 MK II can be had from a trusted seller 2Juki for $330. If higher output is needed then the Denon DL110 is in the low 200's. Output voltage is higher, but not as high as a typical moving magnet. You MIGHT have to add a bit of volume from where your typical volume setting was for the Sumiko cartridge, but it will work. These are the two most affordable moving coil cartridges I am aware of. Otherwise you are looking at moving magnets, typically the Audio Technica AT95 family, or the 540ml which costs in the mid to high $200's. 

@elliottbnewcombjr In the sub $500 new cartridge market I am interested in knowing what options there are for boron or other hybrid cantilevers. For awhile there was carbon fiber but that was more of a cheap as chips option for Audio Technica. 

@neonknight

The Nagaoka MP200 sports a nude elliptical on a boron cantilever, and is well within that range. It’s tougher to find, but I see an MP300H for very close to $500.

@elliottbnewcombjr In the sub $500 new cartridge market I am interested in knowing what options there are for boron or other hybrid cantilevers. For awhile there was carbon fiber but that was more of a cheap as chips option for Audio Technica.

Boron is not common at this price point, even used. Audio Technica makes one that’s (sort of) close - OC9XML, $600 new. There should be various used AT’s with boron out there. You can sometimes find a used Benz Ace or Glider at this price (boron, with either Fritz Gyger or Japanese MicroRidge stylus). A brand new Ace used to cost $550 (circa 2000s) but those days are gone and these models are no longer common.

That said - aluminum cantilevers can sound very, very good. Sometimes even preferable to boron, depending on the cartridge!