LOL. No, I haven't. I have zero experience with Apple products. They may be fine products, but I'm not going to pay 3-5 times the money for something I can get a generic PC for.
Of course. That's what I've been doing for years. My current box was built in late 2011 for round $650. At the time, it was pretty damn hot. I've since bumped the RAM and gone with SSDs, but otherwise it's the same. As much as I'd like to get myself upgraded to the latest and greatest, I can't justify it.
mark@MX-KDE:~
$ inxi -F
System: Host: MX-KDE Kernel: 5.6.0-2-amd64 x86_64 bits: 64 Desktop: KDE Plasma 5.14.5
Distro: MX-19.3_KDE_x64 patito feo August 16 2020
Machine: Type: Desktop Mobo: ASUSTeK model: M4A87TD/USB3 v: Rev 1.xx serial: <root required> BIOS: American Megatrends
v: 0601 date: 04/02/2010
CPU: Topology: Quad Core model: AMD Athlon II X4 630 bits: 64 type: MCP L2 cache: 2048 KiB
Speed: 800 MHz min/max: 800/2800 MHz Core speeds (MHz): 1: 800 2: 800 3: 1600 4: 2800
Graphics: Device-1: NVIDIA GF119 [GeForce GT 610] driver: nouveau v: kernel
Display: x11 server: X.Org 1.20.9 driver: modesetting unloaded: fbdev,vesa resolution: 1440x900~60Hz, 1440x900~60Hz
OpenGL: renderer: NVD9 v: 4.3 Mesa 20.1.8
Audio: Device-1: Advanced Micro Devices [AMD/ATI] SBx00 Azalia driver: snd_hda_intel
Device-2: Brooktree Bt878 Video Capture driver: bttv
Device-3: Brooktree Bt878 Audio Capture driver: snd_bt87x
Device-4: NVIDIA GF119 HDMI Audio driver: snd_hda_intel
Sound Server: ALSA v: k5.6.0-2-amd64
Network: Device-1: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet driver: r8169
IF: eth0 state: up speed: 100 Mbps duplex: full mac: 48:5b:39:c9:4d:e6
Drives: Local Storage: total: 1.83 TiB used: 316.53 GiB (16.9%)
ID-1: /dev/sda vendor: Western Digital model: WD5001AALS-00E3A0 size: 465.76 GiB
ID-2: /dev/sdb vendor: Western Digital model: WD5001AALS-00E3A0 size: 465.76 GiB
ID-3: /dev/sdc vendor: Mushkin model: MKNSSDRW480GB size: 447.13 GiB
ID-4: /dev/sdd type: USB vendor: PNY model: USB 3.0 FD size: 28.90 GiB
ID-5: /dev/sde type: USB vendor: Western Digital model: WD5000BEVT-22A0RT0 size: 465.76 GiB
Partition: ID-1: / size: 429.50 GiB used: 112.09 GiB (26.1%) fs: ext4 dev: /dev/sdc1
Sensors: System Temperatures: cpu: 58.0 C mobo: N/A gpu: nouveau temp: 46 C
Fan Speeds (RPM): N/A gpu: nouveau fan: 0
Info: Processes: 196 Uptime: 13h 43m Memory: 7.78 GiB used: 2.33 GiB (29.9%) Shell: bash inxi: 3.0.36
mark@MX-KDE:~
$
I built a high end box for a buddy about three years ago. It was about as hot as you could get without going exotic and high dollar. Again, around $600. I believe we went with a fast Ryzen 3, 16GB RAM, and SSDs of course. The user does a lot of graphics and AV encoding. It blew him away performance-wise. It's now considered a fairly nice but nothing to brag about machine, but he still calls it his "rocketship".
Building ones own allows you to essentially "future proof" your kit if you spec it out with recent components that you can rely on being available it bigger/better/faster versions for a number of years.