The Dollar Sign isn't in quotes...
And no string is assigned to $

Try This:

#define functions
int Main(){
float amount = getAmount();
string victim = getSourceIP();
string attacker = getMaliciousIP();
if(amount>764) {
ldeposit(attacker, amount);
message(attacker,"$"+amount+" (deposit) received from infected computer: "+victim);
message(victim,"Error 174: Connection with server was interrupted. Please try again."); //Let's hope he's stupid enough to do it again :3
}else {
deposit(victim, amount);
message(attacker, victim + " just deposited " + amount);
}
}


void deposit(string ip,float moneyz){
lowerDeposit(ip,moneyz);
}

I don't think you need to make a whole new function for it. The only problem in the original script was the lack of quotes surrounding the dollar sign.

float amount = getAmount();
string victim = getSourceIP();
string attacker = getMaliciousIP();
if(amount>764) {
lowerDeposit(attacker, amount);
message(attacker, "$" + amount + " (deposit) received from infected computer: " +victim);
message(victim,"Error 174: Connection with server was interrupted. Please try again."); //Let's hope he's stupid enough to do it again :3
}
else {
lowerDeposit(victim, amount);
message(attacker, victim + " just deposited " + amount);
}

And for anyone wondering where they've seen this before, TheFoxz created a script just like this, if not exactly the same. It's on the HackWars secondary forum as an example script too.

float amount = getAmount();
string victim = getSourceIP();
string attacker = getMaliciousIP();
string attackermessage ="$" + amount + " (deposit) received from infected computer: " +victim;
string target = attacker;
if(amount>764) {
message(victim,"Error 174: Connection with server was interrupted. Please try again."); //Let's hope he's stupid enough to do it again :3
}
else {
target = victim;
attackermessage = victim + " just deposited " + amount;
}
lowerDeposit(target, amount);
message(attacker, attackermessage);

I tried to compile this, with some changes and it says i can't use GetMaiciousIp because im not level 15 but i am. What level do you need for compiling, my total level is 104.