Thank you @EggertEnjoyer123 and @Bicurico for sharing your thoughts. I agree with @Bicurico's categorization of users (A,B,C) and which tier they should generally buy. Nevertheless, I think it would be useful for many users to understand specifically what they need each tier for given the big cost steps.
Consider tier 1: I've owned several generations of TinySA; initially, they were just a curiosity; the idea that you could look at RF spectrum with a $50 device that fit in your shirt pocket was nuts. However, their limitations precluded most practical applications (at least above HF/VHF). However, each generation improved (RBW, amplitude/freq accuracy, etc.) and despite the many well documented limitations, I now often grab my TinySA Ultra FIRST when I want to see if an IoT device is transmitting at roughly the right level or frequency or is frequency hopping properly; I often don't care whether the signal is +20 or +22dBm, I just want to know it's in the general vicinity. Similarly, when I want to quickly check the resonant frequency of an antenna, I often grab the NanoVNA SAA-2N out of the same desk drawer. Although I haven't used it for this purpose, from what I can see, the NanoVNA is quite capable of sweeping filters, tuning antennae, characterizing components, and many of the most common VNA applications through 3GHz *as long as high accuracy and big dynamic range isn't necessary* (and it often isn't).
My tier 2 gear comes out when I am spending significant time building/measuring/debugging something and must make precise amplitude/frequency measurements below 3GHz. This is mainly for accuracy and convenience. In the past, I mainly used cellular field service gear from eBay (MT8222a, E7495, etc.), but now I grab my SVA1032x; its capabilities are similar: tracking generator, good amplitude and frequency accuracy (and the ability to slave it to a lab standard), extensive suite of automated measurements, but it is new, calibrated, has a bigger screen, modern UI, easier PC interfacing, etc. all of which make it quite useful for most of my practical RF development and testing. If you use an SA or VNA often or for work and your time is valuable, tier 2 is an easy decision, but for hobby/home use, I suspect that the large majority of practical use-cases for both SA and VNA can now be handled using the combination of TinySA4 and NanoVNA at a much lower price. If you can think of important practical tasks below 3GHz that can be done with tier 2 gear but not with the Tier1 SA+VNA combo, I'm interested in them...that's really what this post is about.
I don't have any tier 3 gear and am interested in where others see it fitting in. Exactly what do you do with it that could not be done with a NanoVNA or SVA? When should a user step up from tier 2 to tier 3?
These days, I only grab my (old, big, heavy) tier 4 gear when I really need to. I mainly use it to prepare for compliance testing when I need to accurately measure (or suppress) spurious/harmonics in protected bands up to 10GHz. I may occasionally use it when I need greater accuracy than tier 2 gear provides, but that is rare. So I agree with @Bicurico about who buys tier 4 gear (user type C), but disagree that tier 4 is mainly a TEA issue; it still seems to be a necessity for testing that must be done before bringing products to the certification lab; I've never been able to get by without a good SA with 10-22GHz BW for this reason.
So @coppercone2, I am not interested in a measuring contest...there are many of those already. The question I'm asking is: what practical tasks can you actually DO with each tier of gear that you can't do with the lower tiers? I've offered a few examples but am interested in more and believe others likely are too.