Why does metro 4 differ from the one in Mallorca?

The metro line of Palma de Mallorca costs one tenth of metro 4, although it is the same length and has the same number of stations – claims a writing full of fallacies and technical errors on the Internet.
While the two projects are hardly comparable, metro 4 costs significantly more – in fact 4 times more with constructions on the surface – due to the followings strictly from a technical point of view.

Passenger traffic:

Metro 4 will be able to transport 16,000 people per hour. The metro in Mallorca carries less passengers (12,000 people) in a whole day.

Capacity:

The metro in Budapest can transport almost two times more passengers (650 people) in one train, than the metro in Mallorca (378 people).

Train succession time:

Trains of metro 4 may follow each-other even in every two minutes, according to busy, downtown requirements. Services in Mallorca go only four times an hour.

Inhabitancy:

Island of Mallorca is a tourist paradise, while Budapest is a several hundred years old metropolis. Many problems of the preparation and completion of metro 4 arise from the densely populated areas. Replacing and mapping of the labyrinth of utilities having been built for 150 years, securing of old town-houses, meeting requirements of residents, lay organizations and municipal offices are a great bureaucratic and technical load, which means delays in construction and increase of costs.

Height:

The metro in Mallorca runs in a depth of 8 m, while the one in Budapest in a depth of 20 m. Therefore the former is a "crust-railway", the tunnel is not bored, but cut, dug from top. This of course is a less expensive solution by magnitudes, but it may be constructed across rarely or not inhabited areas. The Millennium underground is a similar structure, which was built, when also the Andrássy road itself was built.

Bedrock:

In Buda the “kiscelli” clay varies in three different consistencies with unpredictable frequency. The softer the bedrock is, the harder to bore within (as stability of the tunnel is less). There is no such problem in the homogeneous rocky ground in Mallorca. Ground of the Pest side will be an even greater challenge, since there silty soils occur alternately with sandy soils. Constant calibration of the drill shields is of course a cost increasing factor.

Ground-water:

As a result of the Danube and a great depth, works are made extremely difficult (i.e. more expensive) by the ground-water always present, which is a non existing problem on the rock-based Mallorca.

Earthworks below the river:

Drilling two parallel tunnels under the Danube being one of the largest rivers of Europe requires exceptional technical training and professionalism. There will be such part, where the shields will near the Danube river bed to 1.5 m. This task will only be taken by such contractor, whose skills need to be paid respectively.

Tunnels:

Metro 4 comprises two separate tunnels, and the metro in Mallorca has only one, which was cut from the top. This latter costs much less.

Archeology:

It is a works slowing factor that on areas of Budapest having a long history archeological findings are frequent, and they need to be secured and explored. Along the route of metro 4 on the areas of Kelenföld station, Tétényi road and St. Gellért square there were smaller exploration, but yet lasting for weeks, months.

On the other hand, under the title of “Concealed details on the metro in Mallorca” another writing, independent from the DBR Metro Project Directorate, is also spreading across the world web, and according to that four months ago the line – after less than half a year operation – needed to be closed down for undefined time period, because at several locations it was leaking continuously.