ssound5rs You do not need to spend money directly to do the voting. Monthly votes can be obtained from purchasing chapters (all across Qidian) the previous month (10 CNY to get the minimum number based on user level, and +1 every subsequent 10 CNY). 10 CNY = 1.50 USD.
Some people can tip 10,000 CNY directly to the book for a monthly vote.
Most people do not do the second option.