Builder not refunding Booking Amount

I booked a property in Maharashtra and paid a booking amount of 1 Lakh Rs. to the builder. There's no agreement to Sale till now, the only documentation done till now is a "Cost estimation sheet" which indicates the overall price of property + taxes etc., along with a construction-linked payment schedule. The cost estimation sheet also contains a clause "Cancellation charge of 1 Lakh". Now, due to personal reasons, we have had to cancel the transaction and the builder is quoting the cancellation clause while refusing to refund the money. Couple of questions: 1. Does the cost estimation constitute a valid contract admissible in court of law or is it just a gimmick by the builder that can be challenged legally. Asking as i have heard from some sources that such cancellation clauses, even if agreed upon earlier by buyer, are invalid till the time an agreement to sale is done OR unless the cost estimation document is registered which is not the case 2. Is there any other legal recourse to claim the booking amount