To get a Hive upvote worth $0.50 at current Hive price of $0.10, you'd need about 300 Hive Power (HP).
This assumes a 100% vote weight on a post with median expected author rewards—value scales linearly with HP but can vary by post popularity and your total VP. For precision, use the Hive Now Upvote Calculator: https://hive-now.com/upvotecalc.html.