What is the value of a Martin Van Buren one dollar coin?

According to the website https://www.usacoinbook.com/coins/5150/dollars/presidential/2008-P/martin-van-buren/ an uncirculated Martin Van Buren dollar coin can sell (asking price) for as much as $4.50.
I had actually never heard of a Martin Van Buren dollar coin, and it is the unusual qualities of this piece of money that makes it valuable to collectors beyond its face value. For example, it is the only piece of US currency ever to have been made showing President Van Buren. It is part of the Presidential Dollar Series but is the last in this series to have had the words "In God we Trust" printed on the rim. For future coins, those words would be printed on the front of the coin.
Van Buren is an obscure president who only served one term, from 1837 to 1841. For that reason, until this series, no one thought to put him on US currency.