You'll need a join table between Products and Suppliers to resolve their many-to-many relationship. You could call it ProdSup or something much more clever.
The join table will have, at minimum:
1. A key field (__kP_ProdSupID), autoenter serial.
2. The foreign product key (_kF_ProductID)
3. The foreign supplier key (_kF_SupplierID)
4. Fields that are unique to this combination of product and supplier. In your case, Cost and DelvDays.
You can then create a portal on a Product form to this join table related by Product ID, and also a portal on Suppliers to this join table by Supplier ID.
If you create a subsummary report sorted by Product and then by Supplier, you will have your report, as requested in your post. In FM10, you can see this subsummary in Browse mode.