This is a tricky one to answer with a direct conversion. The values are generally lower, for example Plate Mail costs about 80% less coins in SaB than in OSE. However rations are over four times pricier in SaB (that is to further increase the focus on survival).
So the best answer is for you to get a feel for the economy and what gear is worth, and think how much impact that treasure is going to have. But as you get used to that, a good rule of thumb is to reduce it on a 4:1 ratio. (1000 gold treasure in OSE becomes 250 GP in SaB).
The cost of plate is the same in OSE as in SAB - 60 gp fyi. https://oldschoolessentials.necroticgnome.com/srd/index.php/Weapons_And_Armour
