3.5k can get security door dy , some security door stainless steel one .

Usually they count by sqft but since urs is just one door maybe a bit higher for transportation since they can't transport many at once to save cost. Also depends on your door design la, if like current one OK la, if got close here close there bend here bend there got pattern complicated design it's more expensive.

I did my whole house semi d 2.5 Storey stainless steel grille cost me RM47/sqft around September 2022

Your door I think about 8' x 5'? So 40sqft. But if door only usually will be higher maybe let's say with all the inflations and surcharge transport maybe 60/sqft. That's about RM2.4k lo. Try get few quotations la lol

It's seem an indoor grill. No need stainless steel. Just make sure it's properly painted. Then will last very long time.

Security door saw many examples like not really that secure
The connection part where its openable are easily hacked
Apartment like this, still must use grill per management design
Yours quite cheap, which area?

Go shop around . The pic u show before mco is like 500rm include manual labour  .

Also beware or China "304“ for layman easiest is use strong Magnet to check, 304 ss is not magnetic

spot weld vs full weld?

Full weld means totally all joint surfaces will be welded?

Some ss 304 can become slightly magnetic through cold working...china 304 is not 304 at all and cannot be classified under international standard SUS304/18Cr8Ni. Those stainless steel with strong magnetic most likely is chrome plated steel, which is not stainless steel at all. The easiest way to identify stainless steel grade is using battery + test liquid, or the most accurate way by spectrometer.

I dont think its fair to put a blanket statement saying, they are not SS, kan.

My cloth hanging that I bought from China, 20 years ago, its still in very good condition. One piece is on balcony and the other is expose outside in our garden. No rusting or fading at all.