@vonharaland: While in Portland, be sure to visit Crossroads Music. It is a multi-vendor record "mall" in a single large room. All used LP’s, a couple dozen individual sellers.
Portland has quite a few used LP shops, some focusing on certain genres. Tomorrow Records has a large Jazz section, and even sells used hi-fi-components (mostly 1970’s Japanese receivers and turntables). Mississippi Records focuses on World music. Music Millennium has used LP’s, but is better for new releases. I go there on every Record Store Day---they get many copies of each title. A lot of more common titles are priced at $5, even when in Mint Condition.
More rare albums are relatively reasonably priced. I just picked up James Burton’s debut solo album for $25. He played in Ricky Nelson’s band on The Ozzie & Harriet Show, then in Elvis’ band, then in Emmylou Harrises Hot Band (more recently on Elvis Costello’s King Of America album). Give a listen to his solo in Ricky’s dreamy Pop song "Young World". To die for! I had the song on a 7" 45 RPM single before The Beatles ever entered a recording studio. George Harrison’s guitar solo in "Nowhere Man" sure sounds like is was modeled on James’ solo in "Young World." Both very melodic and musical.
Here’s James:
https://youtu.be/Umz2GJR2LLc?si=Maos8KsnR_iox6GF
And Here’s George:
https://youtu.be/8scSwaKbE64?si=DWnxAytz7GssfiPy

