Im totally freaking out cause my sister's wedding is in three weeks and my 50mm just died. Im stuck choosing between MPB, KEH, and just biting the bullet on a refurb from Canon directly. My budget is strictly under 300 bucks. Which of those used sites is actually gonna ship fast enough so I dont miss the big day...
TL;DR go with Canon direct refurbs. Honestly, I once had a lens show up from KEH way late, total nightmare! Canon refurb shipping is lightning fast and the quality is basically brand new. Just grab a Canon EF 50mm f/1.8 STM before they vanish. It is an amazing little lens for weddings and super affordable too. You really cant beat that peace of mind when the big day is so close!
Regarding what #1 said about "TL;DR go with Canon direct refurbs. Honestly, I..." - totally agree on going direct for speed, but I wanted to add that you should snag a Canon EF 50mm f/1.8 STM right now if it's in stock. I bought mine refurbished from them last year and it arrived in like two days flat! Plus it costs way under your budget at around 125 bucks, leaving you extra cash for coffee during the wedding prep.
In my experience, you actually dont need to panic too much about shipping times if you grab the Canon EF 50mm f/1.8 STM right now. MPB and KEH both ship pretty fast with expedited options, but Canon direct is definitely the safest bet for speed since they usually use FedEx overnight or two-day. Since your budget is strictly under 300 bucks, you could also easily score a used Canon EF 50mm f/1.4 USM on MPB for around 200 if you want a slightly brighter aperture for those dimly lit reception venues. Just make sure you select the fastest shipping at checkout no matter which route you pick. You got this, dont stress too hard!