It is no secret that modern aircraft are expensive pieces of equipment. Typically costing tens, if not hundreds of millions of dollars, they represent significant investments for the people or groups that choose to acquire and operate them. But which are the priciest?

The most expensive of all time

Sitting at the top of the tree for the world of aviation as a whole, the Northrop Grumman B-2 'Spirit' is widely recognized as having been the most expensive aircraft of all time. According to Airforce Technology, this United States Air Force stealth bomber originally had a unit cost of $737 million. This figure was valid at the time of its 1997 entry into service.

However, the cost of the aircraft, of which production began in 1987, extended beyond this already astronomical sum. Indeed, the procurement costs of the B-2, which first flew in January 1989, totaled a reported $929 million in equipment, retrofitting, software support, and spare parts. The years of testing involved in the B-2's development also added up.

With all things considered, the program cost per aircraft stacks up to an eye-watering $2.13 billion. With 21 having produced, this represents a hefty bill for the US taxpayer. The grand total could have been even higher, had Congress not cut the order from 132 to 21 B-2s.

Pricey private jets

Most of us will probably never get to experience the exclusive glamour of flying onboard a private jet, let alone owning one of these special aircraft. Such planes often represent a greater investment than the standard versions of the airplane upon which they are based, since buyers can exhibit a greater degree of customization over their new aircraft.

Had it come to fruition, the most expensive private jet ever would likely have been an Airbus A380 ordered by a Saudi Arabian prince. Air Charter Service reports that this would have cost more than $500 million. However, it was ultimately never delivered. As such, the priciest private jet (per Air Charter Service) is, instead, a lavish Airbus A340-300. Owned by Alisher Usmanov, its price is estimated at $350-500 million.

Standard airliners by list price

In terms of aircraft that you and I are more likely to fly onboard, Simple Flying explored the list prices of Airbus and Boeing jets last year. Of course, in the case of list prices, it is worth noting that airliners rarely pay the full price, and instead receive bulk discounts. In any case, Airbus's most expensive airliner was, until recently, the Airbus A380.

The superjumbo, which is now no longer in production, had a list price of $445.6 million. In terms of Airbus jets still in production, the priciest is the A350-1000, at $366.5 million. Meanwhile, Boeing's most expensive commercial aircraft by list price is, unsurprisingly, its 747-8. The newest version of the jumbo jet costs $418.4 million by this metric. However, at $442.2 million, it will be overtaken by the 777-9 when this twinjet enters service.

How many of these aircraft have you ever seen or flown on? Do you have a particular favorite? Let us know your thoughts and experiences in the comments!