That's just because the price you put under goods.ini for the sabre itself is just the cost of the hull. The shield which comes "free" whenever you buy a sabre adds its cost to the sabre's cost also.

i.e. Say the Sabre's cost is 500,000, and the shield which comes with it costs 120,000. The total cost showsn is 620,000. If you lower the cost of the sabre to 5,000, the total cost will still be 5k+120k=125,000.

At least I think that's how it works.

How would I go about finding what shield it has through the .ini files?

First, find your ship in the shiparch.ini. Then find the ships nickname like "ge_fighter6" in that section (that'd be the Eagle in this case).

Then go to the > goods.ini < and locate that nickname in there. You should find a section like this:

[Good
nickname = gf6_hull ; <----- the HULL nick
category = shiphull
ship = ge_fighter6 ;<-----the string you searched for
...

third, do another search in the goods.ini for the HULL NICK specified up there (gf6_hull) and you will find a larger section further down with a lot of
"addon = ..." lines.

One of those addon lines should look like this:
...
addon = shield01_mark07_hf, HpShield01, 1
...

so finally, the "shield_01_mark07_hf" is the nickname of the shield that your ship will have when you buy it. If you want to change it, choose another shield nick, if you want to modify the of shield itself (make it stronger or so), you have to look for that shield nickname in the st_equip.ini.

hope that helped,
D_R