It's not that doing it with VCOs is costly...it's the whole concept itself. Full polyphony means that you have a fully-independent synth under the control of each voice signal, so you have to replicate the VCOs, VCF, VCAs, EGs, LFOs and so on over and over until you arrive at your final output mixer, where you'll mix the different voice signals together for a single mono or stereo output.
The next step down from this isn't actual polyphony. It's something referred to as 'paraphony'; each set of sound generators is controlled by a single voice signal, but instead of replicating the rest of the audio and control chains per voice, the mixdown to a single signal happens after the VCOs, then this goes through a single VCF, etc etc chain to the output. This method actually makes more sense in a modular context, since you can branch and recombine all sorts of paths along that post-VCO chain for sonic variation and arrive at a more controllable (and affordable!) system as a result. This is what I'd recommend as an approach, as a true polyphonic modular is, by default, going to be very spendy and also hell to patch and control. Think something along the lines of Junkie XL's MU 'wall' or Hans Zimmer's monster wall rig of Moog, PPG and Roland modules.
-- Lugia
Thank you for answering and sorry for the late reply.
Yes, a paraphonic instrument is what I need for starters. I've done a lot of research and concluded I'll start with a wavetable module that does chords too (leaning towards Shapeshifter).
This way I will have a patch for chord duties along with external sources for my live needs, and I guess will be a good starting point overall..
I've decided to invest in a 14u/96HP flight case with lots of clean power and low noise and start with 10 or modules, already above budget but functional enough. After that I guess I'll try and fill it slowly and wisely.
Except if I win the lottery. Then it will be sth like 6 Bateleurs for a chord drone and a monster rack for modulation only
Wish me luck