On plating, two things posively affected the plating which I know was done in the past but are relevant today. (1) Looking back to my late father's cleaning of his razor he scrubbed it with a small wire brush akin in size to a toothbrush - bye bye plating. That has carried over to the present time but we use an actual toothbrush which is soft. (2) Polishing it with Brasso. In the army new brasses, mainly belt buckles arrived in a state of pitted and dull. We polished them by rubbing them on cardboard with Brasso on it and the pitting was removed and the brass smooth.
I own stainless steel razors most recently a Yaqi Romulus and I don't support your standpoint that stainless steel is warmer than brass. In my opinion the only metal that I know of that's colder than stainless steel is pewter.
Lastly there are manufacturers still making razors in brass and plated brass. Staying on topic, amongst Chinese manufacturers/sellers look on Aliexpress for "Yintal" = they have brass and plated brass DE razors but watch out for the copper razor which is actually brass plated in a copper colour. In fact I have never seen a Yintal razor which is not brass but I am not saying they don't exist.
Regarding your position on casting stainless steel: Well, the alternative method of manufacture is stamping with a die. But oh well, my stainless steel cutlery must be CNC machined then.
Lastly, a Merkur clone which is priced at more than double the price of the original? Even one made of Stainless Steel? No way!
What you said about maintenance is might be a contributing factor - lots of people don't care for maintenance whatsoever, and even if they do, they can go overboard.
Still, plating needs to be done reasonably well to be worth it - we can see this with zamak razors, too, and the more expensive ones usually have noticeably better plating.
Yintal only use plated brass for handles - the heads are actually coated/plated zamak to look like aged brass. They do actually say so in some of their listings, too. That coating does seem to be more durable than their chrome plating, though (mostly by nature of their chrome plating being too thing and just not very good).
No metal is warm or cold by itself. What I said is that steel holds heat better than brass, but it will take a longer time to bring to the same temperature just due to its lower heat conductivity.
When you were comparing how well brass and steel holds heat, have you actually gotten them to the same temperature, and were you comparing the same razor design (e.g. Karve CB in brass against Karve CB in steel)?
I think you might have left out that I said casting on the cheap is challenging without bubbles. I should have put more context to it, I suppose.
In the post I originally quoted, you said it was cast, not stamped, though.
When you're bringing stamping into it, then that changes things quite significantly - you can have really well made, nearly bubble-free cast steel produced in large quantities for relatively cheap. That's a lot less likely to happen in a comparatively small custom production.
Take a look at Fendrihan's cast steel heads for an example. Perfectly acceptable for actual use, but comparatively worse finish to MIM or CNC machining.
Regardless of whether it was machined or cast, though, the finish appears to be very good, and high quality custom casts aren't going to be cheap either, so as long as they produce the razor to a high standard, the production method isn't very relevant for shaving.
Producing anything from steel to a high standard in small quantities is likely going to be expensive regardless of the method of choice.
The Avanti actually has some clear machining marks on the inside of the lather trough in some of the user submitted photos.
It's only a partial clone, too - the way the head clamps the blade is pretty different from how Progress does it, and that is going to make a difference in how it feels.
Most AliExpress listings have shabby descriptions, so, seeing as the manufacturing method clearly matters to you - why not shoot them a message to clarify?