to find the product cost price from direct SQL query you need to join it from these tables:
product.template
product.product
ir.property
For example:
select temp.name, prop.value_float
from product_template temp
left join product_product pp on pp.product_tmpl_id = temp.id
left join ir_property prop on prop.res_id = 'product.product,' || pp.id
where temp.name = 'Corner Desk'
and prop.company_id=1
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