It looks more expensive per kilogram and usually is not per unit of delivered function. The comparison only becomes meaningful once you convert the dried product back to its fresh equivalent and add the costs that fresh onion carries and dried onion does not.
Step one: get onto the same basis
Drying removes the great majority of the mass of an onion as water. A dehydrated product therefore represents a large multiple of the fresh crop that went into it, and the exact multiple depends on the cultivar’s dry matter content and on the finished moisture target. Convert using the rehydration ratio your supplier states for the specific grade, not a generic figure, and then compare.
Step two: add the costs that only fresh carries
- Preparation yield loss. Topping, tailing, peeling and trimming remove a substantial share of the delivered weight before anything reaches the recipe. You paid freight and duty on that share.
- Labour and equipment. Wet vegetable prep requires a separated area, drainage, cleaning regime and staff. In a dry blending plant that capability may not exist at all.
- Waste handling. Onion waste is wet, odorous and has a disposal cost.
- Shrinkage and spoilage. Fresh bulbs sprout, soften and mould in store; dried product does not.
- Freight and storage. Fresh onion is mostly water occupying chilled or ventilated space. Dried onion is ambient and dense in solids.
Step three: allow for dosing precision
Fresh onion varies in strength between lots and seasons, so recipes built on it either accept flavour drift or carry a compensating adjustment step. A dehydrated product specified against a pungency band lets the formulator hold a fixed dose. Where a plant is running long production runs against a tight sensory specification, that stability is worth real money even though it never appears on an invoice line.
When fresh genuinely is cheaper
Where the buyer is close to a growing region, already has wet prep capability and staff, is producing at a scale where the prep line is well loaded, and the product benefits from raw onion character. Those conditions describe a lot of regional prepared-food manufacturing and very little of the industrial ingredient trade.
What to ask a supplier
Ask for the rehydration ratio for the exact grade, the moisture and water activity targets, the pungency figure on a dry basis, and the pack format and pallet configuration. Those four answers let you build a delivered-solids comparison that survives scrutiny. The onion powder specification guide sets out the full clause list, and the garlic version of this question covers the same ground for the other allium.