The Air Force has admitted to spending a whopping $10,000, a piece, to replace toilet seat covers, in an expense that is being widely criticized, on a Vietnam-era C-5 Galaxy cargo plane.

The reasoning behind the astronomical price tag is that the plane is no longer in production, so custom parts come at a custom price, with the government purchasing the latrine covers at that cost at least three times- and as recently as just last year.

The Washington Post reports Sen. Chuck Grassley, R-Iowa, lashed out at the Defense Department over what he called a 'spare parts rip-off' in a letter to the DoD's Inspector General Glenn Fine.

Grassley is pushing for an investigation into the exorbitant expenditure on the latrine parts and is criticizing the assistant Air Force secretary of acquisition, technology and logistics, Will Roper.

In the letter, which he made public last week, he wrote: 'Thanks to Mr. Roper... we now have, some 30 years later, an on-the-record updated price for a new airborne toilet-related item — $10,000, and that's just for the cover.'

He called the expense 'not credible' and 'in need of scrutiny.'

The part is described by the Air Force as a 'cover-center wall, troop compartment latrine . . . required to protect the aircraft from corrosion damage in the latrine area.'

A $10,000 toilet seat cover: Air Force admitted to buying the part at the sky-high price tag at least three times over

The toilet seat cover, or as the Air Force lists it as a 'cover-center wall, troop compartment latrine . . . required to protect the aircraft from corrosion damage in the latrine area' will be now be 3-D printed

Galaxy C-5 (pictured) is a Vietnam era cargo plane that is still in use, but no longer in production, so spare parts are custom made

The Air Force says it has now come up with a cheaper solution to save taxpayers dollars.

'We are not now, nor will we in the future buy that aircraft part at that price, because we can now do so more cheaply using 3-D printing,' Air Force media relations chief Ann Stefanek told the Post.

'Using this new process allows us to make parts that are no longer in production and is driving major cost savings.'

Roper reasoned to ABC News, 'You'll think, there's no way it costs that.'

'No, it doesn't, but you're asking a company to produce it and they're producing something else. And for them to produce this part for us, they have to quit producing' what they're making now, he added.

'They're losing revenue and profit. So although it looks like it's a certain price in the GSA [Government Services Administration] catalog, the business case is what drives it up. I don't think that company wants to stop building what they're building' and restart the toilet seat line.

The Air Force says they are also working on 3-D printing for other items that typically come with sky-high price tags.

View of a latrine area on a C-5 Galaxy that is no longer in service at the Air Mobility Command Museum

In a statement, Kathie Scarrah, with the Department of Defense's Office of Inspector General (OIG) says they 'have performed a large volume of oversight work associated with waste, fraud, and abuse related to spare parts pricing and has made numerous recommendations for corrective actions.'

She added criminal investigations relating to pricing have also been recommended.

'In addition, we have issued 44 audit reports related to spare-parts pricing,' Scarrah said.

'In the majority of those reports, we determined that the Department of Defense (DoD) did not receive fair and reasonable prices for spare parts and that the DoD did not perform adequate cost or price analysis when it purchased commercial and non-commercial spare parts.'