TBI stands for TOPHOTELPROJECTS Benchmark Investment.
This is an automatic calculation of the investment in million US Dollar that includes: region, country, stars category, size of the construction and, of course, the number of rooms.
Property prizes etc. are not taken into account. The TBI is calculated automatically as soon as the above mentioned factors are entered into the database.

TBI is not for reliability as it is not the actual value, but rather to give you a sense of how the project value might be.