quick construction and Labor price question

HI, so my assassins have decided to build a couple of buildings inside of a town for easy escapes and fun.
but he have found a obstacle concerning labor, for example we pick a townhouse. worth 1200 gp.
now he also have to get the labor for building it. according to the domains at war book labor cost is basically even to the construction price.

now since my assassin don't own the land where his building the house. he cant just order a bunch of people to build stuff.
so since he have to hire and pay the labors the total price for the house gonna be 2400 gp for the materials and the labor cost combined.

is this right? it seems a little strange any chance i can have a verification on if we are doing this right?
or an explanation on the right way to construct building and managing labor.

-thanks

The cost of materials accounts for up to 25% of the total cost of the structure. (Domains at War Campaigns page 51).

However, if you purchase materials, the labor cost is reduced by the amount you paid for the materials.

This means that, unless your ability to purchase materials is restricted or if you already have materials or can get a better deal on them than list price, the only thing you need to know is that it costs 1200 gp to get that townhouse made.

Material and labor costs can be split up if, for example, you looted some lumber from a dungeon and already have it on hand, or if for one reason or another you have limited ability to purchase material. In cases where you’re in a city, and you can hire people and purchase materials without issue, it just costs you the amount that it costs.

D@W:C pages 50 and 51 have examples about this.