1400€ = $2,050US
900mm = 35.43"
It would be interesting to see your complete drawing set for details. You did not state what the material thickness is, or the width (I’m guessing 200mm +/- ). It is difficult to see if the “kink” details are hard creases, or radii.
As a prototype part:
The large radius at the top not withstanding, it is a simple enough form. Judging by the hole pattern running down the exterior face of the panel I will assume that the “end panels” will have a return flange to accommodate fastening them to the exterior. The detail at the top radius of the end panel, where this flange is - will the flange stop (to accommodate the end radius), or do you require it to be continuous around the radius (to be water tight)? If continuous, add forming time. Without the benefit of laser cutting capability, the “grill” pattern would take a quite a bit of time; either drilling (preferred for this closely spaced pattern) or punching (lots of deformation and work hardening by the punching operation); is this detail on both ends? If so double the effort. If this end panel was a stamped piece in production the return flange would not be as troublesome. But as a fabricated piece there would be some fitting of material and welding required to form a continuous flange. More time.
Two (2) units required; six (6) pieces total (two shrouds, four end panels); you mentioned that your quote did not include the adapter case(s).
For talking purposes, based on the size of the piece, I am guessing that you will be specing at least a thickness of .093" [2+mm]. Using that figure your stainless is going to cost roughly 165€ ($240USD); remember the length of the stock is twice the height and then some. That leaves 1,235€ for labor.
Using an average US shop rate of $80 (55€) per hour - if you divide the 1235 by the 55 shop rate that gives you roughly 22+ hours of fab time. Granted this is a very simplified analysis, but it sounds like a reasonable quote given the detail work required.
So, where did you get this quote? A model shop? How about going to a craftsman that does stainless sinks and counter work. Or an HVAC company; heating, ventilation & air conditioning.
Laser cutting the parts (especially the grill patterns) would definitely be the course to take. Forming the large top radius of the exterior, and the flanges of the end panel(s), without benefit of a sheet metal break would be difficult to do accurately; and if you don’t get the angles spot on nothing is going to fit. If this were a “mock up” the fabrication requirements would obviously be much less critical.
If it were me, I’d pay the 1400€. You are not going to become a precision sheet metal boffin overnight, and the amount of wasted time, material, and effort should be another project consideration.