Ok, making a solid shaft with low-grade steel (by modern standards, hand-worked steel is mediocre at best in most applications) wouldn't be as easy as making a thin rod of the same weight as the wood. To get the most out of a steel shaft, so that it's in some manner superior to wood, you have to get fancy with it. Make it hollow, make it shaped like an I-beam or a C-channel, that sort of thing.
For a weapon's handle, to keep both weight and strength in mind, your best bet is to reinforce a wooden haft with steel strips. The weight doesn't have to increase by a large percent, and the end result will be at least as strong as a blade. After all, blades are built tough, but they are still rather thin, so they must be flexible or else they will break when struck on the flat.
The trouble with metal reinforcement is the extra expense, usually, because one of the advantages of a spear is that you can manufacture, say, ten of them for every sword, so you can equip an army ten times as large for the same cost in time and materials. For an adventurer, just go ahead and reinforce your haft. Double the expense (at least, but you can afford it for your single weapon), add %20 to the weight (or %50, if the math is easier that way), and give it the hardness of steel with a little more than the HP of wood.
Bingo, done. I voted "other".