I agree. The problem, if there is one, is there are so few true 50's. The BME 50 was left out of the bunch. The OP built the poll around 50cc engines so the inclusion of any engine exceeding that displacement is probably out of line. However, there are engines with more displacement that weigh less than any of the 50's noted, and there are engines of slightly larger displacement that weigh considerably more than any of those listed. 3w 55 is a perfect example.

Any of the engines listed could have it's base max output altered with a correctly matched and tuned exhaust system. That seriously skews the price and output. So where is the line drawn for a true comparison? No exhaust? In many cases is would be less noisy in a dyno test than with the stock mufflers. A DA on stock muffs drives me out of the shop when it's running on the dyno.