Seems relatively reasonable to me, especially because the Canucks' pick isn't necessarily going to be 29th, it could be anywhere from 25-32 (25th if all 4 division winners lose this round). By the Athletic's pick values, pick 5 is 8.2 GSVA. I looked through 18 trades moving up in the first round and on average they gave around 10-20% over the value in return, so somewhere between 9.02 and 9.84 is the rough estimate of what it would cost, assuming the Habs were willing. Pick 9 is 6.3 GSVA and 29 is 3.0 GSVA and 9.3 is right in that range. In the unlikely scenario where it ends up as 25th that's 9.7 GSVA and if the Canucks win the cup it's 9.0. Obviously any trade like this will happen once the pick placement is known, but it really seems about right to me.
Considering in this case the Habs are trading back because they want a forward and they (accurately in this mock) think the next few players off the board will be d-men, essentially they lost nothing since their target was still there at 9 and they added a free late first.