Denon 103S is a real good cartridge

I've been using an EMT TSD15 and I'm in the process of replacing it so I bought a 103S and it's very satisfying. Remarkably so. I'm now questioning if spending big money on cartridges is really that necessary? Of course I'm not listening side by side :)
The world is replete with excellent cartridges that don't cost a fortune. The answer to your question is self-evident: No. But, on the other hand, expensive cartridges don't necessarily sound bad, either.
I loved the EMT but my system needs have changed so I'm going with a Lyra Delos. I was using it on a Well Tempered Simplex with a Herron VTPH-1 loaded at whatever was recommended. Can't remember.
Are you referring to the DL 103SA that is out of production? The 100th Anniversary DL A-100 is still available and appears to be very similar to the 103SA, including a nude square stylus. It's also about $162 cheaper.