I've always wondered this. Even if you have $10k USD worth of BTC, you still need to find someone to buy it? What if you wanted to cash out $100k or $500k? At that point you need legal contracts, escrows, 3rd party verification, etc..

Yes, I used breadwallet to sell some bitcoins, accidentally set the transaction fee at (what I'd later find out to be) ~10 satoshis/byte.

Now I have ~$2300 locked up in the mempool, and no end in sight for these high transaction fees. Can't figure out a way to raise the fee.

https://jochen-hoenicke.de/queue/#4d

It should expire in 3-4 days. You can also try importing the keys to another compatible wallet and redo the transaction with higher fee.

Thanks! Currently trying to find a wallet that will let me double spend. Any recommendations?

Actually I don't think any wallet will let you do that. How ever, you can install breadwallet on another phone/device (don't mess with your existing one) and restore with your backup seed (12 or 24 words one). Electrum is another good wallet for desktop that supports all kinds of seed words where you can again import your seed words and re-spend them. The newly installed wallets will let you spend it again because it has no way of knowing that you already spent it.

Good luck.