Yeah you’re right, I wasn’t factoring in the cost of Ableton. That just about doubles it.
Don’t for a second thing that there’s any reason to pay the premium for a Mac if you do go the computer route, though. MAcs are fine, but the idea tha they’re superior to any other similarly specced hardware or modern operating system is 100% marketing. Macs are solidly built (except for every few years when they have a bad run of them, like the well known macbooks from around 2006 that had SMD parts that weren’t soldered correctly and would frequently stop working unless you literally attached a clamp to them or stuffed wooden shims between the motherboard and case, or otherwise figured out a way to keep pressure on the loose components sot that they would maintain contact with the board) Intel based PCs running a proprietary build of BSD, nothing more and nothing less. Depending on the brand and model, the major components (motherboards, screens, etc.) of macs and PCs are often literally manufactured in the same factories.
You can cut 30%-40% off of your cost if you go with an equivalent Windows or Linux based system (the latter is a bigger hassle but still feasible).
But yeah, the price of Ableton will put you well over the cost of an Octatrack for sure. I use Reaper and secondhand Windows machines, so for me a perfectly solid computer based performance rig would be maybe 2/3 the cost of an Octatrack MKII if that, unless I needed high end converters (which the Octatrack doesn’t have either, so that’s not a fair comparison).
EDIT: I strongly agree that an OT MKI would be a better choice, but it depends on what kind of workflow you’re after.
Personally I recognize that Ableton makes a very powerful program but I wouldn’t even pay half what they charge for it when you could use something like Usine or Renoise or Reaper or Reaktor or Bitwig Studio or Sunvox or Buzz or any number of other programs that may have very different workflows but are just as capable in their own ways.
I also wouldn’t trust a computer running a general purpose OS in live performance.
And finally, there’s the issue of a closed system vs an open ended system where you never truly master the environment and workflow because it is constantly changing, but that’s an argument better left to neuroscientists and cognitive psychologists.