I see you are in Canada. We cannot answer why Jump+ was quoting you $129, only Jump+ can tell you why.
In another reply you asked
"I called apple directly instead and they’re “express replacement” was $129 (plus a $2000 hold on my credit card). So would that mean once they “assess” it…they would credit me back $$??"
Express replacement gets you a replacement phone upfront so it's the full other damage AppleCare+ fee of $129 because you return your damaged phone. If you did a in-store visit or mail in repair and they only replaced your back glass giving you the same phone you already had back it would be the $39. So no, if you do an express replacement, you will not be refunded the difference between $129 and $39, but as long as you return your damaged phone within the time period they state the hold on your credit card will be dropped
#4 at the bottom of AppleCare Products - iPhone - Apple (CA)
"Express Replacement Service is not available under the screen replacement or back glass damage service fee. Same-day service availability and options may vary by region and iPhone model. For international service, Apple may repair or replace your iPhone and iPhone parts with a comparable iPhone model or parts that comply with local standards. Service coverage is subject to AppleCare+ Terms and Conditions. See AppleCare+ Terms and Conditions for complete product details."