Baseball America has a table up listing how much each team is allotted for the 2012 June draft.
The Astros are allowed to spend $11,177,700 on Rounds 1-10.
As BA explains:
Any team that exceeds its bonus pool by 0-5 percent must pay a 75 percent tax on the overage. The penalties escalate, with a 75 percent tax and the loss of a first-round pick for a 5-10 percent overage; a 100 percent tax and the loss of first- and second-rounders for a 10-15 percent overage; and a 100 percent tax and the loss of two first-rounders for an overage of 15 percent or more.