Where the difference goes
Cost to company is what employing you costs, which is a larger number than what you are paid. The employer's provident fund contribution — typically 12% of basic — is part of CTC and goes to your PF account. Gratuity accrues and is payable only after five years of service. Group insurance premiums are paid to an insurer.
None of that is dishonest, and all of it is genuinely yours or spent on you. But it means a ₹12 lakh CTC does not divide into ₹1 lakh a month, and someone budgeting on that assumption will be roughly 20–30% out.