It is all about Youtuber and the mobile company.Youtube starts paying them when you achieve required number of subscribers and watch hours, i think itu2019s like 1000 subscribers and 4000hours of watch time, then you must make Google Adsense and add ads to your videos.Tech reviewers are either asked by companies or ask companies themselves for some products to review. Then the product is yours and thatu2019s sort of way of earning money, by Youtube ads and the products from reviews.