The Linq 'groupby' is not really a SQL group by, but a method which results in a set of sets. Your Select therefore tries to create a set of sets, and this is seen as a set of nested queries (one for each set) and it therefore needs to tie each nested set to a parent row, with a correlated predicate. However, what you want to do isn't creating a set of sets, but a single select with a where that limits the rows based on another query.
You really have to specify how the table or tables involved look like, and e.g. what 'priceQueryable' is. You talk about prices and points, and these aren't the same.
So I assume it's as simple as the Orders table in Northwind where I'll fetch the orders for each customer with the latest orderdate. Your query likely looks the same, more or less. It helps if you write it out in SQL first or at least know where it'll need to go, especially with Linq, as constructs like groupby aren't really mappable in a 1:1 fashion to SQL.
the sql query becomes:
SELECT A.*
FROM Orders A
INNER JOIN (
SELECT CustomerId, MAX(OrderDate) MaxOrderDate
FROM Orders
GROUP BY Customerid
) B ON A.CustomerId = B.CustomerId AND A.OrderDate= B.MaxOrderDate
and in linq this will become
var metaData = new LinqMetaData(adapter);
var q = from o1 in metaData.Order
join o2 in (from x in metaData.Order
group x by x.CustomerId into g
select new { CustomerId= g.Key, OrderDate = g.Max(v=>v.OrderDate)})
on new { o1.CustomerId, o1.OrderDate} equals new { o2.CustomerId, o2.OrderDate }
select o1;
var results = q.ToList();
Notice the same column names in the elements in the on clause in the join. If the names differ, the code won't compile as the anonymous types differ and the C# compiler gives up.
I don't know the specifics of your table, so you might need to adjust it here and there. It helps if you write the query out in sql first in this case, as it's not trivial, plus not all constructs to solve this problem in SQL are available in linq (they are in queryspec, our other high level query system btw).
Btw, you're using an old runtime/version, it's recommended you upgrade to a later runtime if possible.