1. Most of the big shot builders make such unreasonable causes whcih suits their object incorporated on the sale agreement.
2. Since most such sale agreement are typically pre-drafted in which the buyer can not make any changes except the description of flats to be purchased.
3. There is conflict of opinion among high courts as to whether on cancellation of agreement the builder can forfeit the whole earnest money or huge percentage out of consideration m0ney already paid. In most case where the court finds that the buyer has no say in drafting the sale agreement it declares such clauses as ' unconscionable'.
4. In any case, if the cancellation amount is huge and is more than the booking amount then the court generally intervenes to set aside such such clause.
5. in the instant case, you can challenge this clause on the consumer forum and ask for refund of the same if not already deducted. I have successfully reversed such cancellation charges from the consumer in several of such incidents made by big real estate companies in Kolkata.