Buying for best value per terabyte, filling a NAS runs from $1000 (QNAP TS-233 2-Bay Desktop NAS Diskless, 2 bays) to $4000 (Synology DiskStation DS1825+ 8-Bay, 8 bays), drives only. That is the best-value figure, not the smallest bill: optimising cost per terabyte selects the largest drive, so it buys far more storage and costs more than a minimum fill. Each model page names both numbers.
Live prices updated · 25 models with a verified bay count
Each row multiplies the cheapest qualifying in-stock drive by that model's bay count. The tiers differ by what qualifies: cheapest takes the lowest cost per terabyte among new CMR-verified drives, enterprise restricts to nearline families, refurbished uses recertified stock. All three are matched to the chassis interface, so nothing here is a basket that cannot physically work in the machine beside it.
The three tiers are not the same build. Each picks the cheapest terabyte within its own rules, and those rules land on different drive sizes - so a refurbished column far below the others usually means a smaller drive, not an enormous saving. The per-drive capacity is printed next to every figure for that reason. Comparing the totals without it is the same error as comparing a 3TB build to a 20TB build and calling the difference a discount. Cost per usable terabyte, on each model page, is the comparison that holds.
Drives only except the final column. A dash means nothing qualifying was in stock at the last refresh - we do not carry a stale price forward to keep a cell populated.
NAS reviews compare chassis. They tell you the processor, the memory, the network speed and the price of an empty box, and then stop - which leaves the reader to work out the part that dominates the bill. A four-bay machine at $600 and a six-bay machine at $840 are not $240 apart in practice: the six-bay needs two more drives, and at current prices that difference is several times the difference in chassis price.
That is the arithmetic this table does. It also makes the bay-count decision visible in the only terms that matter at purchase time - not "how many bays do I want" but "what does the next two bays cost me today, filled". Cost per usable terabyte after parity, on each model page, is the sharper version of the same comparison, because parity overhead falls as bay count rises and a bigger box is often cheaper per usable terabyte despite costing more.
Interface and form factor matched to the chassis, CMR-verified, in stock at page load. We exclude shingled drives outright, and we also exclude drives whose recording technology we could not confirm rather than assuming them safe - an SMR drive in a rebuilding array is the most consequential wrong recommendation this site could make. The CMR/SMR list shows how each model was verified.
Prices are our tracked figures. Amazon sets the seller and the final price at checkout, so treat every total here as an accurate estimate of what a basket costs rather than a quote. Where a manufacturer publishes a drive compatibility list, that list is the authority on what the vendor has tested, and each model page links it rather than paraphrasing it.
NAS devices compared · NAS drives by price per TB · NAS builder · RAID usable capacity calculator · Recertified drives · Cheapest per TB
Across the 25 models we track it currently runs from $1000 to $4000 for a full set of drives at the cheapest qualifying tier - the spread is almost entirely bay count, since a two-bay box needs two drives and an eight-bay box needs eight. Enterprise and refurbished tiers move the figure in either direction. The table above carries every model with today's numbers.
Because a NAS is a small computer and the drives are the storage. A four-bay chassis is a CPU, some memory and a power supply; four large drives are four precision mechanical devices in a market that has been supply-constrained through 2026. At most capacities worth buying, the filled cost is dominated by the drives, which is exactly why the chassis price on its own is a misleading way to compare machines.
Not necessarily, and there is a real argument for staging. Standard RAID sizes to the smallest drive, so a partial fill you later top up with larger drives wastes the difference until every drive is replaced. Buying all bays at once with matched drives avoids that. The counter-argument is cash and drive-batch risk: some builders deliberately buy from different batches so a manufacturing fault does not take every drive at once.
The comparison column marked "with chassis" does; the tier totals do not. We separate them because plenty of people reading this already own the box and want the drive number, while plenty of others are pricing the whole build. Each model page shows both, itemised.
They are read from our catalogue when the page loads, and the catalogue refreshes every few hours from live listings. In-stock only: a model whose drives are all out of stock shows a dash rather than a stale price. The timestamp at the top of this page is the last successful refresh, not the moment you happened to arrive.