Cheapest for me was the Packard Bell Pack-Mate 28 Plus for $17 (tower, keyboard, and mouse) which needed a new clock battery, and I had a few parts lying around (CD drive, RAM, dual floppy drive, joystick, data tape drive, and sound cards), so I installed those parts to make it as a Multimedia system.
Did some upgrades along the way:
1) Upgraded the CPU from the SX2-50 to the DX2-66, and later upgraded to a DX4-100 OverDrive (5V CPU only)
2) Upgraded the HDD from the 428.1MB Seagate to the 2GB CF Card (didn't work out too well), then to the 4.6GB laptop HDD (2.5" to 3.5" IDE kit)
3) Upgraded the sound card from the Aztech Sound Galaxy NX Pro* to the SB16 CT2740 with a Yamaha DB50XG board
4) Upgraded the CD drive from the 48x (acted up constantly) to a 52x CD drive with a headphone jack and playback controls (with the volume wheel) for playing Audio CDs without using software
* Still have and re-soldered with wires jumping to the corresponding spots (capacitors and chipsets)
Specs:
Intel i486 DX4-100 OverDrive (33MHz x 3)
PB450M motherboard (OPTi 82C802 chipset) BIOS Revision PB450MP+ PNP release 1.1A <-- will upgrade to a later version (Y2K friendly)
32MB SIMM-72 memory (upgradable to 64MB), also has 4MB on-board, but that's disabled
Cirrus Logic CL-GD5428 1MB vRAM (expandable to 2MB)
Packard Bell Keyboard and Mouse
Conner 170MB/350MB (compressed) internal tape drive <-- Thrift store find (new)
Epson SD-800 Dual Floppy Drive (1.44MB 3.5" and 1.2MB 5.25") <-- got last year
Delta 52x CD-ROM drive <-- Thrift store find
Fujitsu 4.6GB Notebook IDE HDD (2.5" to 3.5" kit) <-- pulled from an HP Pavilion N3350
Creative Labs Sound Blaster 16 CT2470 with the Yamaha DB50XG Daughterboard (PeterNY) <-- AmiBay
Music Quest MPU-401 clone card (keropi) <-- AmiBay
Gravis Analog Pro joystick (4 buttons (2 programmable), throttle, manual adjusters, and fire button) <-- eBay
Tandy 3-voice Compatible Sound card <-- eBay: texelec
3Com EtherLink III 3509B-TP (RJ45/AUI) ISA Ethernet card <-- installed by original owner
Discord: https://discord.gg/U5dJw7x
Systems from the Compaq Portable 1 to Ryzen 9 5950X
Twitch: https://twitch.tv/retropcuser