I did the same but it still took almost a week to get my $$. Though I've heard shipping with their labels saves some $$, I did not notice savings anywhere near 50%.
If you take it to a UPS storefront instead of a hub, they often add a surcharge. I was facing $60 shipping from them as far back as 2010. it got to the point where shipping from the East Coast to anywhere west of the Rockies was over $100 as recently as 2016, when I stopped doing that.
Even now, when I buy the label, they show me how much to ship by USPS and FedEx. What will cost $45 through Reverb will often cost $70 at Fedex and $100 at USPS. Even shipping from here to Seattle or LA has been just $60. I haven't gone in to UPS to see what they would charge without Reverb since 2016, so I'm just projecting from the past to the point I wouldn't be surprised with a $120 bill to ship to the West Coast. Bolstered by a guy who shipped me a Cali from Seattle and showed me a $115 shipping receipt. I've even had like $37 shipping from here to as far away as Alabama.
So, I'd like to point out, that I did say "often", not every time like clockwork. Also, I didn't do comparison shopping. It is entirely possible 50% is only compared to the higher options. I recognize they might not be showing the real price when they show the comparison, because they want me to use their label, but I bet it isn't that far off.
Finally, whether it is actually 50% or just 45% at best, I've just noticed that shipping is much more reasonable via Reverb shipping labels. Since it took me a few years to realize that was a worthwhile move, maybe someone else needs to hear it, so I was just sharing my impression.
I'm sorry if you feel I was misrepresenting your impression or somehow shilling for Reverb. I'm getting tired of seeing the price my customers pay compared to how much I get in my pocket, but a good part of that is because now Reverb charges taxes, which inter-state taxation for online shopping is, I think, one of the worst development in the history of the internet. But also not Reverb's fault, but I should just stop here.