At this point in time, if you want power, longevity, and reliability in a twin cylinder engine you pay the price for those attributes. Currently the only "budget" brand that has reasonable quality standards is DLE. It would only require a day of research and reading to learn why not going for the cheap makers would end up saving a lot of money and distress in the long run. So you have a choice: Buy cheap but get it now, or save your money until you can buy it once.

Low price should never be the pinnacle point to base a qualified decision on. A great many people have learned that the hard way. Currently the available selection of 50cc twins is severely limited. D&B might still make one. You might still find and old 3w-48 or small BME twin around on the used market. For the moment there are not any Chinese twins in this size I would buy regardlss of how inexpensive they were. I prefer to buy it and fly it instead of fussing for months trying to fix it, if it could be fixed.