Why is solar field cost equal for all solar systems?

Dear SAM Community,
Hi, I have a few questions.
In the "(2015) Parabolic Trough Collector Cost Update for the System Advisor Model (SAM)",
1) The difference "HTF System ($/m^2)" old value cost of "Molten Salt Linear Fresnel Model" and "Direct Steam Linear Fresnel Model" is understandable but why "Solar Field ($/m^2)" old value cost is different for them?
2)why "Solar Field ($/m^2)" new value cost is equal for all solar systems(PTC, LFR, CSP Power tower)?

Your quick response is highly anticipated.
My best regards.
Sadegh.

dear Paul

The text mentions that the author did not have access to the cost of Solar field of LFR. Therefore, Solar field of PTC and LFR costs considered are the same, but since the cost of the solar field of LFR is lower, the upper limit of the cost of LFR is considered equal to PTC cost.
I want to compare two of these systems together.
If the prices of both the same, Unlike the published articles, due to better PTC efficiency, it would be better to use PTC collector, economically.
Do you think the following approximation can be used?

In the text, 95% of the price of the PTC is related to raw materials. It seems that due to the simplicity of LFR construction Compare to PTC, this percentage is higher for LFR. which is assumed to be the same as 95% here.
old cost of PTC:270
new cost of PTC: 170
old cost of LFR: 170
New cost of LFR=(old cost of LFR)*[1-(old cost of PTC - new cost of PTC)/old cost of PTC*0.95]
New cost of LFR=110 $/m^2