Yes, the "suggested" lamps are there because the sellers paid to boost the listings.

As for insane prices, tell me: how much does a carbon filament lamp cost? They haven't been produced since the '40s or '50s and they have been banned for a couple years now.

It comes down to simple economics, my friend: supply is low, but demand is also low, the price will remain low. The price would only skyrocket if everyone suddenly decided they
wanted to transition back to MV and such, in which case they would probably start producing them again.

carbon filament lamps were made into the 70s. Maybe even 80s.

Currently, in the US, "Soft white" is the equivalent term to "Warm white" aka 2700-3000K.
With incandescent and halogen lamps, "Soft white" referred to lamps with white finish or diffused lamps.

Was this at the AZ-143 and I-10 interchange?

With choke ballast fluorescent stuff you can leave the ballast in place. Because the LED current is significantly lower than from the original tube, this gives you only a small amount of ballast losses. Ideally you'd just remove it altogether.
With HF ballasts LED tubes it's a whole special thing and you need to leave it in place. But this is a very  unwise thing to do. HF drivers last a long time but by now most of them are over 10 years old and you maybe have a reliable 10 years of life left in them. HF ballast LED tubes also cannot usually be connected straight to mains so in 10 years time you'd have to start searching for new HF fluorescent ballasts i guess.

Agreed both of you! Things do taste great fire burnt, but I’d literally eat Marshmallows in every form!

Yes, but the two meanings of "Soft White" have been present as long or nearly as long as the term itself.  For example, here is a soft white fluorescent dating back to 1946.  I believe that's around the same time as the soft white incandescent lamps were introduced, although whether the phrase was ever used prior to Q-Coat, I'm not sure.  Another ambiguous term is "Full Spectrum".  It's typically a cooler colored lamp with better color rendering than the original daylight, but there is no criteria for what spectra qualify.  One that has popped up in recent years is "Bright White", referring to lamps in the 3000K-3500K range, and is even being used by Philips now.  This is worse than some of the others given that brightness already refers to luminosity at a distance.  At least softness and even fullness don't have technical meaning the same way brightness. 

Nowadays, when people hear soft white it’s the color temperature. Back in the day, soft white actually just met the finish. A soft white bulb had a soft white coating, a clear bulb had no coating, and an inside frost bulb had either a very thin soft white coating or acid etching. This was the case for years with incandescents and halogens.

Many soft white fluorescent tubes were called “warm white” rather than soft. It was warm white, cool white, daylight for most brands. But suddenly, soft white now has nothing to do with the bulbs finish. Most 2700K clear LEDs are still called soft white.

What do you think about this?

In most of the streetlight retrofits I've seen, the Cap and Ignitor are removed, because just cutting the wires and undoing a nut is all it requires, but the ballast is left (with cut wires). I believe this is because the nuts holding it on are generally much harder to access, at least in the reftofitted fixtures I have.

@RRK
I wonder if they ever experimented with ceramics for these instead of quartz

Yep, adding some halides (CaI2 or NaI) to correct that ugly greenish tint immediately brings this creation into realm of metal halide lamps, arctube corrosion will straight away chop off 2/3 of that hyped 60K hours lifetime. Right?

As one internet meme said "Overcomplicated solutions for non-existing problems"