According to Baseball America, the Pittsburgh Pirates will have a draft bonus pool of $7,392,200 in 2015, which ranks as the 11th highest in baseball. The Pirates don’t make their first selection until the 19th pick, but they have a compensation pick(32nd overall) for losing Russell Martin to the Toronto Blue Jays, so that pushes them closer to the top of the list. As noted in the article, the draft bonus pool across baseball increased by 8.7% over last year.
The total this year is more than $300,000 higher than they had last year. In 2014, they exceeded their bonus pool by nearly 5% when they signed 11th round draft pick Gage Hinsz and they went over the previous year as well when they signed Erich Weiss(each was the last player to sign). They ended up paying a 75% tax on the overage each year, but kept it under 5% over their cap which kept them from incurring more severe penalties. The penalty for going over by more than 5% is the loss of a first round pick and a 75% tax on every dollar over the pool total. The penalties get more severe the higher you go over the pool total.
You can read more about the penalties in the link above, although no team has exceeded their pool by more than 5% since the new rules were put in place three years ago.