This is a general guide for how much a Tunnel Boring Machine (TBM) would cost. It is not realistic to give exact figures in ever changing marketplace, but certain factors effecting TBM prices generally remain constant. Therefore it is better to mention the factors effecting the price of a TBM.

Remember that, when you want to buy a TBM, you don't have any showrooms of TBM Manufacturers to visit. Almost all the time, TBMs are custom built, after they are ordered. 

The cost of a tunnel boring machine (TBM) basically depends on the following parameters:

• TBM Diameter

The boring diameter of a TBM is an important factor in determining its price. As a general rule (with occasional exceptions), one can assume that as the diameter increases, so does the price tag. But the this increase is not really linear. There is also an exemption for subway-size TBMs.

An often quoted general rule of thumb for the price of a Tunnel Boring Machine is; US$ 1 million for per meter in diameter. Thus, a TBM of 8 meter in diameter would cost around US$ 8 millions. In reality, the increase in price is not so linear as the diameter increases.

For smaller-diameter TBMs, you will often see that the increase in price will be lower than a million dollars per meter. And as the diameter increases, especially from "subway size" to bigger diameters, the price differential for each meter increase in diameter will be more than a million dollars. Especially for the large diameter TBMs used for multi-level, multi-track, multi-lane tunnels, the price per meter will be much higher, as such an increase in diameter comes with some exponential increase in technological complexity. It is not just "bigger size of the cutter head" from the point of TBM design and technologies.

Economies of scale play in pricing

There are some exemptions to this "the bigger, the costlier" paradigm. It is just a matter of economics. Certain TBM diameters (e.g. so-called "subway size" of around 6 meters of diameter) are high in demand. Therefore they are produced by more numerous manufactures and in greater numbers. Hence in turn, their spare parts, like the main bearings of this size are often available off-the-shelf and at competitive pricing. As a typical TBM consists of around 10-15 thousand parts, economies of scale also works here. For that reason, a "subway size" TBM may occasionally cost less than a smaller but custom-size TBM.

For this reason of 'economies of scale', the price increase from the "subway size" to say, 7 meters will not be a linear increase.

Increased competition

Prices of TBMs have come down rather radically in recent years mainly because there is more competition, more TBM manufacturers and more TBM production nowadays. In the past, Tunnel Boring Machines were mostly produced in the USA, Japan, Germany, France and Canada. Nowadays the list includes Turkey, Korea and most importantly China.

The entry of Chinese manufacturers to the TBM manufacturing has been quite a disruption for the TBM market. In the very positive sense. Thanks to Chinese manufacturers, the prices of TBMs have come down rather radically in recent years. Before China's TBM manufacturers flooded the market with World-class TBMs, the cost was around US$ 1,5 million per meter in diameter. Nowadays with some Chinese TBMs for "subway size" this can be as low as US$ 700-500 thousands/meter.

• TBM Type

Tunnel Boring Machines are produced for various geological conditions and their complexity varies accordingly. As expected, the more complex a TBM is, the more expensive it will be. For example the cost of a single shield mixed ground TBM that you use in uninhabited areas is usually the lowest. On the other hand, if you need to bore a tunnel under a sprawling city center, you'd better use an Earth Pressure Balance (EPB) TBM which will be more expensive. For certain geological conditions, there will be a need to use Slurry TBMs which generally tends to be even more expensive.

• TBM Manufacturer

Like everything else, there are buyers who are prepared to pay extra for a certain brand. This may be due to some perceived level of quality for a familiar TBM brand which has been around for decades. People are understandably timid in trying out a new brand even if it offers a better price/performance ratio. And this allows the established brands to charge extra for their products and service.

Of course, there will be many cases when a certain brand will be offering a better quality at a higher price. You pay what you get for.

• Project Prestige, Market Considerations

Sometimes manufacturers go to great lengths to supply a project with Tunnel Boring Machines by offering attractive price/performance packages. There might be several reasons for this.

For one, a tunneling project might be a prestigious project which is often a great marketing coup for the manufacturer. For a brand established in that market, it will be yet another showcase and for a less established brand a validation of brand opportunity.

In other cases, a manufacturer may give discount to defend their turf in the market. Or in other cases, it may be a priority for a brand to break into, to get a foothold in a certain market. For example, a manufacturer which has never delivered a TBM in a west European country, may be willing to make an extra attractive offer to get their TBMs selected.