Originally posted by ChristianRock after my beloved K-S1 developed aperture block failure
For reference, note that your K-S1 will still work fine with any KAF4 lens, like the 55-300 PLM, and it will also work fine in Manual Mode with any older lens that has an aperture ring (K, M, A, F, FA).
KEH.com regularly sells used K-3's for $450 or less with a 6 month warranty (12 month warranty if purchased before Dec 31, 2020). They currently have one EX+ K-3 priced at $429 in stock. I purchased a EX K-3 from them about 6 months ago: it was in great shape and has worked without trouble through some heavy use.