I have purchased many CPU's on eBay, and almost all of them have been used. I have a lightly used, never overclocked Intel Q6600 for sale for $100 (shipped) BTW...
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Intel DZ77GA-70K
OS
Microsoft Windows 8.1 Enterprise 64-bit
CPU
Intel(R) Core(TM) i7-3770K CPU @ 4.7GHz (Overclocked)
Motherboard
Intel Corporation DZ77GA-70K, 0066 BIOS version
Memory
32 GB 12800 DDR3 Crucial Ballistix Sport
Graphics Card(s)
NVIDIA GeForce GTX 660 SC x 2 (SLI) by EVGA
Sound Card
(1) Bluetooth Hands-free Audio (2) NVIDIA High Definition
Monitor(s) Displays
LG 27" HDMI
Screen Resolution
12920 x 1080 x 32 bits (4294967296 colors) @ 60Hz
Hard Drives
Intel 120GB SSD (ATA INTEL SSDSC2CT12 SCSI Disk Device)
Western Digital Caviar Black 64M cache 2TB 7200rpm (ATA WDC WD2002FAEX-0 SCSI Disk Device), 3 x WD 150Gb 10k Velociraptor hard drives in RAID 0 (testing)
PSU
Corsair 750w fully modular
Case
Corsair 650D with perforated side panel
Cooling
3 200mm case fans, Intel liquid cooling for CPU w 120mm fans
Keyboard
Logitech backlit
Mouse
Dell
Internet Speed
11Mbps DSL
Antivirus
Windows Defender, MalWareBytes Pro and CCleaner Pro
Be sure the seller lets you return a "DOA" piece of hardware. I've never had a single issue and I've been buying and selling on eBay since 12/98. There are many good sellers and buyers on eBay, just look for them and check their feedback.
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Intel DZ77GA-70K
OS
Microsoft Windows 8.1 Enterprise 64-bit
CPU
Intel(R) Core(TM) i7-3770K CPU @ 4.7GHz (Overclocked)
Motherboard
Intel Corporation DZ77GA-70K, 0066 BIOS version
Memory
32 GB 12800 DDR3 Crucial Ballistix Sport
Graphics Card(s)
NVIDIA GeForce GTX 660 SC x 2 (SLI) by EVGA
Sound Card
(1) Bluetooth Hands-free Audio (2) NVIDIA High Definition
Monitor(s) Displays
LG 27" HDMI
Screen Resolution
12920 x 1080 x 32 bits (4294967296 colors) @ 60Hz
Hard Drives
Intel 120GB SSD (ATA INTEL SSDSC2CT12 SCSI Disk Device)
Western Digital Caviar Black 64M cache 2TB 7200rpm (ATA WDC WD2002FAEX-0 SCSI Disk Device), 3 x WD 150Gb 10k Velociraptor hard drives in RAID 0 (testing)
PSU
Corsair 750w fully modular
Case
Corsair 650D with perforated side panel
Cooling
3 200mm case fans, Intel liquid cooling for CPU w 120mm fans
Keyboard
Logitech backlit
Mouse
Dell
Internet Speed
11Mbps DSL
Antivirus
Windows Defender, MalWareBytes Pro and CCleaner Pro
As long as you buy from an Ebay seller with a good reputation, there shouldn't be a problem. I've bought cpus, ram, OSes and other items from Ebay sellers without issue.
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Home Built desktop, Dell G15 5511 Gaming laptop,MS Surface Pro 7 tablet
OS
W10 Pro desktop, W11 laptop, W11 Pro tablet (all 64-bit)
CPU
3.7Ghz 8700K i7, i7-11800H, i7-1065G7
Motherboard
ASUS TUF Z370-Pro Gaming in desktop
Memory
16G desktop, 16G laptop, 4G tablet
Graphics Card(s)
AMD Radeon RX580, RTX 3060, Intel Iris Plus
Sound Card
High Definition Audio (Built-in to mobo)
Monitor(s) Displays
Samsung U32J59 32" (2x), 15.6", 12"
Screen Resolution
3840x2160, 3840x2160, 1920x1080, 2160x1440
Hard Drives
500G SSD for OS; 2T, 10T & 15T HDDs for Data on Desktop, 1TB SSD laptop, 128G SSD tablet.
PSU
Corsair CX 750M
Case
Antec 100
Cooling
CM 212+
Keyboard
IBM Model M - used continuously since 1986
Mouse
Microsoft Pro IntelliMouse
Internet Speed
400M down 8M up
Antivirus
Windows Defender
Browser
FireFox
Other Info
Built my first computer (8Mhz 8088cpu, 640K RAM, 20MB HDD, 2 360K floppy drives) in 1985 and have been building them for myself, relatives and friends ever since.