ODROID-HC4 is a 65$ 2 bay network attached storage device

From Liliputing.com: ODROID-HC4 is a 65$ 2 bay network attached storage device.

SATA HAT

From Radxa.com: SATA HAT for Raspberry Pi 4 and ROCK Pi 4. Comes in dual quad and penta versions.

Benfei USB3 to 2.5inch SATA adapter cable

Amazon sells the Benfei USB3 to 2.5inch SATA adapter cable for less than 8$.

Sabrent USB3 to 2.5 inch SATA adapter

Amazon sells the Sabrent USB3 to 2.5 inch SATA adapter for less than 10$.

QNAP SilentNAS HS-453DX

The QNAP SilentNAS HS-453DX is a silent but powerful fanless multimedia NAS with hybrid storage structure, 10GbE connectivity, and HDMI 2.0 4K output, all for less than 700 Euros.

Inateck 3 port USB3 hub with 2.5 inch SATA enclosure case

Amazon sells the Inateck 3 port USB3 hub with 2.5 inch SATA enclosure case for less than 26 Euros.

Samsung unveils 2.5 inch 16TB SSD

From ArsTechnica.com: Samsung unveils 2.5 inch 16TB SSD.

2TB 2.5inch hard drive 9.5mm high

Today I received my first 2TB 2.5inch hard drive (9.5mm high) with SATA interface. So small, yet so big! Biggest wow factor! Just ordered another four of them for replacing some old back up drives! Update: as the internal version costs nearly 150 Euros and not available anywhere, I got myself the Dell 784-BBBD Portable Hard Drive 2TB, USB 3.0, an external hard drive which includes the case, SATA2USB3 adapter and the USB3 cable, all for less than 90 Euros! Takes about one minute to open the case and remove the drive to use it as an internal drive for any computer, that accepts 9,5mm thin 2,5" SATA drives.

newertech Voyager Q hard drive dock

newertech sells the Voyager Q hard drive dock with USB3, Firewire and eSATA interfaces for less than 72$.

RaidSonic IB-2222SSK

RaidSonic sells the IB-2222SSK to put four 2,5" hard drives (up to 15mm thickness!) into a 5,25" slot for less than 100 Euros. IMHO no port multiplier built in!

DawiControl one to five SATA port multiplier

DawiControl sells the DW-6510 PM, a one to five SATA port multiplier for less than 100 Euros.

Lindy one to five SATA port multiplier

Lindy sells a one to five SATA port multiplier for less than 100 Euros.