According to the Samsung Concierge customer service dude I'm speaking to at the moment regarding replacement of the back cover/panel due to a crack I noticed, he said:
"The estimated cost for the back cover replacement is approximately SGD$120. Do take note that there will be a SGD$32.10 for service & labour charge.
Exact price will be advised to you upon evaluation been done by our technician."
Thanks to Samsung Concierge, price will be halved, including the service and labour charge, so the customer service dude confirmed that it will be SGD$76.05 total the entire back panel.
I did check that since I have up until May 16th 2019 to benefit from my Samsung Concierge out-of-warranty 50% Savings on repairs, I can still continue to use the phone as it is not a big deal so far, and since I may incur further damage to the phone during this time, I might as well wait as long as possible before using this one-time half-price home-visit repair.
I also asked what the price is for repairing of the s9+ front screen and LCD, just in case I damage it during this period.
Official Answer:
The cost for replacing the screen of S9+ is approximately SGD$370.
The screen replacement would be inclusive of the screen + LCD together.
I suppose that means in the worst-case scenario, if my front screen gets damaged too, before a year elapses on my purchase date, I can get a full repair on the front and back panels, glass and LCD display for SGD$261.05 (after the 50% discount), and the technician will come to my home to do it, too.
Hope this helps, first time using the site.
Cheers,
Rey