Not cheap,, but maybe cheaper than nixie tubes. Simple hand held calculators were just coming out at around $150 at the time. How do I remember? A snotty nosed know it all fat kid's dad bought him the first calculator in the school. He brought it to school and was showing off with it. I bet him I could calculate faster than he could with the calculator, lol! Our math teacher was a known betting man and thought it was a great idea so he had us turn our backs to the chalkboard and wrote down about a dozen calculations, each dependent upon the results of the prior calculation. Ready Set Go! We spun around and proceeded to calculate, the red faced porky kid's forehead beaded with sweat and dripping off his nose as he feverishly poked his fat finger into the keys, my pencil was a flying. I finished about 5 seconds before he did. The teacher asked me what my answer was and I told him. Then he asked the porky kid and he gave a different answer. Mine was right, he was wrong! LMAO! The whole class had a good laugh. I'll never forget.