DIY in your mind:
1. Buy bare PCB for $20 plus $100 in parts.
2. Assemble.
3. Get $1000 in performance for $120!
DIY in the real world:
1. Buy bare PCB for $20 plus $100 in parts.
2. Realize that you ordered the wrong parts, pay return shipping plus new parts, add $50.
3. Realize that hey, while you're at it, might as well upgrade some parts, add $250.
4. Get a good soldering iron, silver solder, flux, solder sucker, board cleaner, third hands, board cleaner, add $200.
5. Realize you need a dremel for a board mod that someone recommended on a DIY forum, purchase dremel, drill bits, grinding wheels, cutters, and add hot air rework station, nice Fluke meter, on-sale oscilloscope, and variac, add $1000.
6. Begin assembly. Realize you still have some wrong parts, so might as well get better ones, plus drawers to organize your parts, plus some more parts for A/B testing later, add $250.
7. Power on. Despite variac, the board smokes. Troubleshoot and buy more parts, plus another Fluke meter to measure current, plus a current-limited lab power supply, plus a function generator so you can visually tell if the circuit is working early in the game, plus a Flir One to see what's getting hot. Add $1,000.
8. Power on, it works. Spend a week swapping parts and listening. Oops, shorted something, board go boom. Spend an evening troubleshooting and replacing parts. Can't find it. Realize you need a 6.5 digit 4-wire bench meter...
And so on...
(Now, before I get eviscerated by the DIY crowd, I have to reiterate I have the utmost respect for DIY...and the lessons you learn while making your own stuff is invaluable. It just can't be thought of as cheap or easy, either in terms of budget or time. If you love it, do it. Just go in, eyes open.)