Mark,
I work at home on my P.C.
I work away using BIAB, my instruments and Reaper until I can bounce it down to what I think is good.
IF my song and mix seem "good" I spend the small amount of cash to have it "mastered" because I can't do that step, for the reasons explained.
I don't do it often.
The difference it makes is amazing.
The difference having an objective pair of ears listen carefully and communicate what they hear is equally amazing.

I suspect the Soundcloud, and other algorithm based, processors are static...IF you're lucky they "listen" to the track, match your requirements to a template and modify the template according to the source the process.
if you're unlucky it'll just apply the template before processing. It's very unlikely they'd shift settings within a track.

The "subscription model" is the new way of milking.
At AUS$1.10 a day for the Izotope bundle seems cheap but it's $1,200 over three years. OUCH.

Cheers
rayc
"What's so funny about peace, love & understanding?" - N.Lowe