Texas has an option fee. Most national calculators miss it.
The option fee is a negotiated payment that buys you the right to end the contract for any reason during the option period, and it is separate from your earnest money. In Texas it is typically $100 to $500, it is due within three days of the contract's effective date, and it is delivered to the title company in escrow, under the TREC residential contract. It is not a fee, it is a negotiated term, which is exactly why most national calculators never show it.
Source: Texas Real Estate Commission