Agree with Tom. What specific application were you thinking of? I've seen HSS occasionally for threading but seems to slowly be phasing out. Less so for straight turning, albeit I wasn't aware of the ones shown at LMS. But yeesh 8.95 USD for one. You can get a 10 pack of carbides with same geometry & many more flavors of material cutting applications, coating, nose radius, chip-breaker etc.
I'm guessing the selling point is the usual HSS vs Carbide discussion: HSS has toughness so theoretically better for lower speeds, interrupted cuts, dissimilar density like breaking through skin even though its usually not quite as hard as carbide. Unfortunately loose lathes or less rigid or real low power machines may fall into this category inadvertently. HSS may help but its not a miracle cure in those cases either. For straight turning, cheapo Ebay/Ali carbides have served me well in a variety of materials. The uncoated ones for aluminum are razor sharp & go for miles before degrading. The coated ones I use for steel, same deal. Most chipped corners are operator induced unless its an ugly material.
For example I ventured into carbide threading inserts last year & was pretty impressed despite running at much lower than recommended SFM. They cut clean with no degradation. These happen to be fine threads (therefore teeny tip radius), stainless steel parts (more challenging material that likes to heat & work harden). On a manual machine sometimes you don't have any other option than to run slower, especially threading, without running the risk of disengaging late & bad things happen. So no, not removing material as efficiently vs. CNC, but those machines are much more robust, have optimized variable rpm & feed control. But that doesn't mean carbides wont still work well for us. You may have to experiment to find the best settings on your setup, but that's almost a given in hobby machining.