Well, let's see who is involved:
Flight 93 National Memorial (U.S. National Park Service)
Here is from the wiki which may or may not be accurate [choose your views accordingly].
On March 7, 2002, Congressman John Murtha (PA-12) introduced a bill in the United States House of Representatives to establish a National Memorial to be developed by a commission, and ultimately administered by the National Park Service. On April 16, 2002, Senator Arlen Specter (PA) introduced a version of the "Flight 93 National Memorial Act" in the Senate. On September 10, 2002 the bill passed both houses of Congress. The final bill specifically excluded the four hijackers from the passengers to be memorialized. When signed by President George W. Bush on September 24, 2002, it became Public Law No. 107-226, and the site was listed on the National Register of Historic Places. By September 2005, the commission was required to send to the Secretary of the Interior and Congress recommendations for the planning, design, construction, and long-term management of a permanent memorial.
The proposed boundaries of the National Memorial extend from Lambertsville Road to U.S. Highway 30. It will be about 2,200 acres (890 ha), of which about 1,000 acres (400 ha) will be privately held, but protected through partnership agreements. The memorial itself would be a 400-acre (160 ha) bowl-shaped area, with 1,800 acres (730 ha) surrounding as a buffer. In December 2002, landowner Tim Lambert donated 6 acres (2.4 ha) at the crash site, and entered discussions with the Conservation Fund regarding 160 acres (65 ha) additional. Using some funds donated from receipts for the film United 93, the Families of Flight 93 organization purchased 3 acres (1.2 ha) in the summer of 2006. The organization is also seeking $10 million in federal funding to use for acquiring land. In November 2006, the Conservation Fund acquired 100 acres (40 ha) as buffer land which are to be managed by the Pennsylvania Game Commission. PBS Coals Inc. sold 900 acres (360 ha) to the families' organization in March 2008.
The Flight 93 National Memorial Campaign is a partnership among the Families of Flight 93, the Flight 93 Federal Advisory Commission, the Flight 93 Memorial Task Force, the National Park Service, the National Park Foundation and many representatives of local, state and national organizations, agencies and interests, as well as people from around the world to build a permanent memorial. Launched in 2005, this public-private partnership is seeking to raise $30 million from philanthropic individuals, corporations and foundations to enable the construction of the Flight 93 National Memorial.
So, it looks like it was planned and the plan executed in the post 9/11 OMG phase of America where rational thought was put somewhat on hold and the "anything for 'them'" was part of the national pride that popped up.
So we have bipartisan support for dropping $28M [although, since they don't seem to have near the $30M in private donations, I assume they will either have to scale back or pony up more than $28M.
Library of Congress PL 107-226