Inventory: Understanding Average Cost

Inventory Simple Case - Avg Cost IS impacted by Sequence!!!

TxType	EFFCTV QTY	ACCUMQTY	COST	TOTCOST	ACCUMBAL	AVGCOST
B	100	100	15	1500	1500	15
S	-50	50	15	-750	750	15
I	10	60	20	200	950	15.83333333

TxType	EFFCTV QTY	ACCUMQTY	COST	TOTCOST	ACCUMBAL	AVGCOST
B	100	100	15	1500	1500	15
I	10	110	20	200	1700	15.45454545
S	-50	60	15.45454545	-772.7272727	927.2727273	15.45454545

Inventory with a sale reversal, but keeping it positive! All good, but sequence matters

TxType	EFFCTV QTY	ACCUMQTY	COST	TOTCOST	ACCUMBAL	AVGCOST
B	100	100	15	1500	1500	15
S	-50	50	15	-750	750	15
I	10	60	20	200	950	15.83333333
S	200	260	15.83333333	3166.666667	4116.666667	15.83333333
I	10	270	20	200	4316.666667	15.98765432
S	-200	70	15.98765432	-3197.530864	1119.135802	15.98765432

TxType	EFFCTV QTY	ACCUMQTY	COST	TOTCOST	ACCUMBAL	AVGCOST
B	100	100	15	1500	1500	15
S	-50	50	15	-750	750	15
I	10	60	20	200	950	15.83333333
S	200	260	15.83333333	3166.666667	4116.666667	15.83333333
S	-200	60	15.83333333	-3166.666667	950	15.83333333
I	10	70	20	200	1150	16.42857143

If sale and reversal are together - it doesn't matter the sequence!

TxType	EFFCTV QTY	ACCUMQTY	COST	TOTCOST	ACCUMBAL	AVGCOST
B	100	100	15	1500	1500	15
S	-50	50	15	-750	750	15
I	10	60	20	200	950	15.83333333
I	10	70	20	200	1150	16.42857143
S	200	270	16.42857143	3285.714286	4435.714286	16.42857143
S	-200	70	16.42857143	-3285.714286	1150	16.42857143