It’s definitely a seller's market right now, mate. Facebook just hit us with a massive ban wave, so good supply is extremely scarce and overall account quality has tanked heavily. Most legit sellers are low on stock and focusing only on their bulk, long-term clients.
Instead of chasing them in the Marketplace, I'd suggest opening a thread in the "Want to Buy" section. State exactly what you need and your budget; reliable suppliers who actually have stock will reach out to you directly. Good luck finding a solid batch!