It looks as if you need an outer join, I’ll use a left one in my example:
select t1.Product, t1.Quantity, t2.Cost
from table1 as t1
left outer join table2 as t2
on t1.Product = t2.Product
You can also leave out the outer keyword:
select t1.Product, t1.Quantity, t2.Cost
from table1 as t1
left join table2 as t2
on t1.Product = t2.Product