Guess the main costs would be the digital interface and software plus a new computer maybe (does it really gave to be a mac!!)
Cheap audio interfaces have come a very long way, I'd look at what's being sold second hand in your area. Something with a Hi-Z input if you're wanting to record your guitars directly though the interface.
I lack quality studio monitors or monitoring headphones with a flat response, they're kind of pricey, but necessary to make professional sounding music. Any speakers or headphones you play your tracks through will add their own sound that makes it difficult to mix or master properly. The tracks might sound great through the speakers or headphones you're using, but like garbage through other ones. With flat monitors, what you hear is only the sounds of your tracks.
For software I use the vast array of audio production tools on linux through kxstudio and elsewhere.
My workflow tends to be, hydrogen for drums, rosegarden patched through various plugins for midi, all routed into ardour alongside any audio input tracks. I'll usually record track by track. I use ardour to mix everything, then I take my mixed down track and master it using jamin.
Didn't read the article, but a Windows/macOS computer with a DAW + audio interface (for recording instruments + if you decide to get nice headphones that require a pre-amp) + midi controller + some virtual synths/samples, and you should be good to go.
There are plenty of decent free synth/samples, so I wouldn't count it as an absolute necessity to spend money on synths.
The only reason I say "Windows or macOS" is because of driver compatibility with your equipment + choice of DAWs, with the most widely used ones being macOS/Windows only.
Even thought you have a piano that is midi compatible, you might want a separate MIDI controller, so that it is smaller + has pads + knobs to control various parameters. I have a piano with MIDI-out as well, but found it to be super inconvenient to work with compared to an actual midi controller. My personal affordable recommendation that isn't just basic barebones stuff is Arturia Minilab MKII (currently $109 on Amazon). Got it myself a couple of months ago, still very happy with the purchase.
Regarding an audio interface, Focusrite Scarlett 2i2 is very robust and is heavily recommended (currently $159 on Amazon). It might be a little bit more than the basic needs, but it gives you a bit of a room to grow. And the basic version is just $109 (Scarlett Solo), so I feel like an extra $50 is worth it, given that you probably won't have a need (but def might be tempted to) to buy another one pretty much ever.
Its my opinion that most folks who are going to be using programmed drums would be better off with an inexpensive MIDI controller with some pads (like the one pictured in your article) vs playing them on an electronic kit unless they happen to be a very skilled drummer.
I play drums passably, but when I'm demoing up ideas I just thump them in with some pads on a MIDI controller.
Note that a separate pre-amp or DI box is not necessary with these. You can connect microphones of either kind directly as well as pickups.
> does it really gave to be a mac!!
No.
> No.
To go further on this, I switched from mac to PC for my studio setup a couple years back as mac hardware seemed to increase in price too much in relation to PC. I had only bought software that was able to run on both because I want to maintain flexibility to switch at will; and switching my commercial VSTs, DAW (Ableton Suite), NI Reactor, etc to PC was seamless. All my saved sets came across fine.
The practice with what you have. Getting good at recording takes years.