"This is too expensive so I'm not buying it."
If I learned one thing from living in China for four years it is that Chinese is a language of brevity. The Chinese simply do not use an excess of words as we do in English. I translated the sentence as follows: "这太贵了，我不买." Yes, its street and colloquial but its real. This is how Chinese people really speak. No need for excess words like 因为 or 所以. Seriously Chinese people try to say the most with the fewest words. It is the ultimate minimalists' language. In Chinese less is more. That's why Chinese love the 成语; only four 汉字！
It's used that way all the time.
This page has 3 examples with 因为 at the beginning http://dictionary.pinpinchinese.com/definitions/s/%E5%9B%A0%E4%B8%BA-yinwei And this one has 5 https://www.yellowbridge.com/chinese/sentsearch.php?word=%E5%9B%A0%E4%B8%BA