Is step-up basis of property sold within 6 months of the decedent’s demise the sale price?

From the Instructions for Form 706 - https://www.irs.gov/instructions/i706

Please read all the instructions for “alternate valuation” and speak with your tax advisor, but by using alternate valuation you can decrease the value of the estate.

Part 3—Elections by the Executor

Line 1. Alternate Valuation

“...Once made, the election may not be revoked. The election may be made on a late-filed Form 706, provided it is not filed later than 1 year after the due date (including extensions actually granted). Relief under Regulations sections 301.9100-1 and 301.9100-3 may be available to make an alternate valuation election or a protective alternate valuation election, provided a Form 706 is filed no later than 1 year after the due date of the return (including extensions actually granted).

If alternate valuation is elected, value the property included in the gross estate as of the following dates, as applicable.

- Any property distributed, sold, exchanged, or otherwise disposed of or separated or passed from the gross estate by any method within 6 months after the decedent's death is valued on the date of distribution, sale, exchange, or other disposition. Value this property on the date it ceases to be a part of the gross estate; for example, on the date the title passes as the result of its sale, exchange, or other disposition.

- Any property not distributed, sold, exchanged, or otherwise disposed of within the 6-month period is valued as of 6 months after the date of the decedent's death.

- Any property, interest, or estate that is affected by mere lapse of time is valued as of the date of the decedent's death or on the date of its distribution, sale, exchange, or other disposition, whichever occurs first. However, you may change the date of death value to account for any change in value that is not due to a “mere lapse of time” on the date of its distribution, sale, exchange, or other disposition.

The property included in the alternate valuation and valued as of 6 months after the date of the decedent's death, or as of some intermediate date (as described above), is the property included in the gross estate on the date of the decedent's death. Therefore, you must first determine what property was part of the gross estate at the decedent's death.”