Case Study 1 — Riverside Foods: Inside the Plant's Cost Structure

This case study takes you inside the Riverside Foods frozen-vegetable processing plant in Millbrook and walks through its real (stylized) cost structure in detail. The goal is to connect the abstract cost curves from the chapter to what a plant manager actually sees when she opens the accounting books.

The plant's monthly cost breakdown

Riverside Foods' plant in Millbrook processes raw vegetables into frozen products. The plant operates a single production line running two shifts (6 a.m.–2 p.m. and 2 p.m.–10 p.m.) six days a week. At full capacity, the plant can process about 2 million pounds of finished product per month. Current output is about 1.2 million pounds — running at about 60% of capacity.

Fixed costs: ~$455,000/month

These costs are incurred whether the plant produces 0 or 2 million pounds in a given month.

Variable costs at current output (1.2M lbs): ~$700,000/month

Note: the "per pound" figures above don't quite match $700K / 1.2M = $0.58/lb because of rounding. The important point is the structure, not the exact cents.

Total cost at 1.2M lbs: ~$1,155,000

Average costs at 1.2M lbs

A 14-cent profit per pound. That's a 12.7% margin on revenue. Not luxurious. One bad growing season (vegetables cost $0.45/lb instead of $0.35/lb) would wipe out most of the profit.

What happens when Riverside scales up

Suppose Riverside increases output from 1.2M to 1.6M lbs/month by adding workers and running the second shift at fuller capacity.

What changes: - Production labor: more workers needed. At 1.6M lbs, about 550 workers (up from 400). Some are on overtime ($33/hr instead of $22/hr). Labor cost rises to about $500K. - Raw vegetables: more input needed. 1.6M × $0.35 = $560K. - Packaging, electricity, gas, shipping: all scale roughly proportionally with output. - Fixed costs: unchanged at $455K.

Marginal cost of the additional 400K lbs:

The variable cost of the additional 400K lbs is higher per pound than the first 1.2M because: - Overtime wages for some workers ($33/hr vs. $22/hr) raise labor cost per hour - The plant is running at 80% capacity — some equipment is running at peak, increasing maintenance and energy costs - Some workers are less experienced (new hires to fill the expanded shift)

Estimated additional variable cost for the 400K incremental pounds: about $275K, or about $0.69/lb — higher than the $0.58/lb AVC at 1.2M.

This is diminishing returns in action: each additional pound costs more because the plant is approaching its designed capacity.

Is the expansion profitable?

• Additional revenue: 400K × $1.10 = $440K
• Additional cost: $275K (variable only; fixed costs are unchanged)
• Additional profit: $165K

Yes. The expansion is profitable because MR ($1.10/lb) exceeds MC (~$0.69/lb). But the margin is thinner than at 1.2M lbs — each additional pound earns less incremental profit.

What happens at full capacity (2M lbs)

At 2 million pounds, the plant is at 100% of designed capacity. Every piece of equipment is running at its rated speed. Every worker is on a full shift. Any additional output would require significant overtime (at 1.5× pay) or weekend shifts (at 2× pay for some workers).

At this point, the marginal cost per pound is very high — perhaps $1.00 or more. If the selling price is $1.10/lb, the margin on the last units is almost zero. Expanding beyond 2M lbs would require capital investment (a new production line, building expansion) — which shifts the analysis from the short run to the long run.

What the case study illustrates

Lesson 1 — Cost structures are concrete. The abstract cost curves from the chapter correspond to real line items: labor, materials, electricity, shipping. Each curve has a shape for a reason rooted in the physics of the plant.

Lesson 2 — Fixed costs are real and large. $455K/month in costs that don't change with output means Riverside needs to produce at least enough to cover those costs before it starts earning profit. At the current AVC of $0.58/lb and price of $1.10/lb, the contribution margin is $0.52/lb. To cover $455K in fixed costs: $455K / $0.52 = about 875K lbs. That's the break-even output.

Lesson 3 — Diminishing returns are visible in the cost data. The marginal cost of producing more rises as the plant approaches capacity. At 60% capacity, MC ≈ $0.58/lb. At 80%, MC ≈ $0.69/lb. At 100%, MC ≈ $1.00/lb. The MC curve slopes upward for exactly the reason the chapter described: diminishing returns to adding more variable inputs to a fixed plant.

Lesson 4 — The profit margin is thin. At 14 cents per pound, Riverside is profitable but not lavishly so. This is typical for food-processing businesses. The thin margin means the plant is very sensitive to input costs, wholesale prices, and demand fluctuations. A 10% increase in raw vegetable costs ($0.035 more per pound) would reduce profit by about $42K/month — roughly a quarter of the current profit.

Lesson 5 — The shutdown rule is not hypothetical. If the wholesale price fell below about $0.58/lb (the minimum AVC), Riverside should shut down: every pound produced would lose money on variable costs alone. If the price fell to $0.80/lb (above AVC but below ATC), Riverside should keep operating in the short run (it covers variable costs and makes some contribution to fixed costs) but plan to exit in the long run when the building lease expires.

Discussion questions

1. Riverside's fixed costs are $455K/month. If the plant shut down for a month, it would still pay $455K but produce nothing. Under what conditions would shutting down for a month make sense?

2. The break-even output is about 875K lbs. What happens if output falls below this level? Is the plant necessarily doomed?

3. Labor is the largest single variable cost. If Riverside automated some production tasks (replacing workers with machines), labor costs would fall but equipment costs (fixed costs) would rise. Under what conditions would the automation be worthwhile?

4. Raw vegetable prices vary by season. How should Riverside manage this variability? (Hint: contracts, inventory, product-mix changes.)

5. A competitor plant opens 50 miles away and starts selling to some of Riverside's grocery-chain customers at $1.05/lb. What happens to Riverside's revenue, output decision, and profit? How should Riverside respond?