So what makes a technically newer brand of typewriter more valuable than an older one?
reply to liamkembleyoung at https://reddit.com/r/typewriters/comments/1v4ykv9/pros_and_cons_of_pre1950s_typewriters_vs_1950s/
Quality of the materials, build, and engineering, condition of the machine (clean, well-adjusted, rubber condition), popularity, rarity, desirability, collectability all figure into machine pricing.
Most would say that the $250-350 Royal Classic/We R Memory Keepers machines from Shanghai Weilv Mechanism Company that are available new from Amazon and other retailers are cheap, poorly made pieces of junk with dreadful quality control and thus not worth the money one would spend on them. (The fact that they sell on ShopGoodWill for $5-10 underlines this.)
You might also have a 1970s Brother typewriter (made in the millions) that might have sold brand new in the $100 range versus a used 1955 Olympia SG1 selling in that same shop at the same time (1970s) for about the same money, or possibly less. The SG1 is acknowledged as one of the finest typewriters ever manufactured versus the very pedestrian and "cheaper" (materials-wise) Brother, so it's going to be worth more money now in the secondary market. The SG1 is less common, has a better reputation, more popular, more collectible, and just a better machine overall which is also likely to last longer. At the low end the SG1 is going to go for $75-150 while the Brother will be $25. Fully serviced out of a repair shop (cleaned, oiled, and adjusted with new rubber feet and a recovered platen) they might go respectively for $700-850 and $400-475.
Keep in mind that most typewriters you'll see on this sub and in the broader market are far from "rare"; rarity and desirability are two different things; and rare doesn't always equate to being more expensive. Actually rare machines aren't often discussed on this sub in general.