I caught my first Steelhead using a $20 reel and $30 rod. By putting in lots of time on the water, I started catching Steelhead more frequently. I used the same setup for years and gained enough experience and confidence to land Steelhead on a regular basis. I saved my money and about 5 years ago I made the ultimate purchase (in my opinion) of fishing equipment. I bought a GLoomis STR1024C rod and matched it with a Shimano Curado reel. The difference was absolutely incredible.

Someone once asked me if it was worth paying five times more for a rod. I answered that I'd rather have one "high quality" rod then 5 average quality rods.

So to answer your question, no it's not necessary to purchase expensive equipment to catch Steelhead. But I feel that my "investment" was worth every penny. I still have my original rod/reel and occasionally use it as a back up.
Mark