Weird, it seems like the opposite case on my place.
o3DS prices are slowly going down almost reaching Wii U prices ($100 average), I remember o3DS prices were between $130 - $240 but nowadays the most expensive o3DS (regular color; not limited edition) I found in the market is $160.
I recently bought one for $50 with its only flaws are the smudge marks underneath the LCDs which aren't noticeable to notice at least; everything else is surprisingly in mint condition despite it being 13 years old (via Mii Plaza; last StreetPass).
New 3DS (XL) prices haven't changed a bit for years (shit doesn't go below $200 unless it's defective

).
It seems like Yahoo! Auction is the only place to buy one in decent condition for less than $200.
I won't deny that the Switch V1/V2/Lite prices recently are crashing quickly, the V1 iPatched units became the cheapest and nobody are buying them if it's above $70. I need to sell my unpatched V1 immediately. (Already have a V2, preparing it for modchipping for better overclocking/underclocking yields than the V1)