[1.7.10]Multiplier for balance should be a double not int

[tytannial]

modifier = Math.max(modifier + Config.modifier, 0); multiplier = Math.max(multiplier + Config.multiplier, 0);

cost = (base + modifier) * multiplier; Negative multiplier is bug in those code. Min cost should be 1 not 0, there need a check for it. Integer multiplier seems useless in reducing materials by percentage.