Renovate house from 1988 - windows and front door?

I have now received an offer for a complete replacement:
A total of approximately 17.7m² window area
Door 1.1m*2.2m + 0.621m window.

9 windows + front door (door alone about €4000) 3-pane glazing from Gayko compact Classic V82 AD Ug of 0.6 Total cost: €16,500 including installation and disposal.
That comes to a savings of about €1000 p.a.

Through a colleague's brother, only the panes to be replaced with warm edge about €1900
Results in a Uw of 1.5 approx. €650 p.a.

Am I overlooking something? Purely based on the numbers, pane replacement makes much more sense.

Window fitters like to offer what brings them more business, which is always the complete replacement. Glass replacement does not create more dirt than can be swept up, and can already be noticeably improved especially with warm edge spacer bars. The innovation of frames in PVC is largely limited to fashionable aspects (rounded edges, narrower sight lines). However, a glass replacement from double- to triple-glazed usually means a glass unit about two cm thicker, so the glazing beads must have that much reserve. After so many years, a seal replacement should also bring a noticeable improvement. The biggest advantage is that you can carry out the glass replacement literally piece by piece. That means you first do the glass replacement on the north side and "invest" these costs as a trial. If the evaluation turns out weak, you can still go for "the big operation."

Additional wall insulation is not economical anyway, as only savings corresponding to a U-value reduction of 0.3 can be achieved, which is about 20 kWh / m² per year with costs around 200€/m².

I quote myself since I have just seen the construction description. Since 17.5 cm (or 24 cm?) of load-bearing masonry + 5 cm insulation (presumably mineral wool WLG 040) + 4 cm air layer + facing masonry have been executed here, one thing would make sense here: blowing the air layer with mineral wool flakes, as long as the exterior wall is rainproof.

Am I overlooking something? Purely from the numbers, replacing the pane makes much more sense.

If your profiles are still good and have a corresponding remaining service life, replacing the pane makes sense. Window replacement to triple glazing is subsidized with a 15% grant; replacing the pane is not.