A2 tool steel is probably at least twice the $/lb price of 4140(?) alloy steel. But the cost difference between A2 and 4140, per part based on the tool dimensions you provided, would not seem to be a significant factor unless you are making this tool in large quantities.
Another thing to consider is that flame hardening will only produce a hard outer case layer. The surface hardness after finish grinding of your flame hardened 4140 tool will likely be <Rc 54. 4150 alloy steel would give slightly better results than 4140 with flame hardening. The 4150 finish ground surface would be a bit harder (maybe Rc 56) and the case would be a bit heavier. A2 tool steel is nice because it is very stable in heat treat, and should require less finish grind stock removal than flame hardened 4140/4150 tools. Something to consider with flame hardening large numbers of parts is that a flame hardening set up usually can only process one part at a time, while the A2 parts can be heat treated in batches.
If you are producing large quantities of this locating cone tool (which sounds like it has an axis-symmetric shape), one thing you might consider doing to reduce raw material and machining costs would be to have blanks roll forged close to net shape. The cost to roll forge a near net shape blank for this cone tool is likely quite modest, and could easily be offset by reduced material scrap and machining time.
Good luck with your project.
