Weigh harvest and record where it goes: sold, held as stock, rejected, used as samples or lost. Split sales by grade and buyer because prices and deductions differ. Revenue from accepted credit sales and cash received are separate measures; an unpaid invoice may be a receivable, not an immediate cash receipt. Returns and bad debts need their own treatment.
Use the denominator that matches your question. Production cost per harvested kilogram describes production. Cost per sold kilogram also exposes unsold and rejected output. Cash collected per kilogram describes collections, not the biological performance of the crop. Label the period so that a payment received this month for last month's crop does not distort this crop's result.