is a i7-6500U based laptop worth the cost to upgrade to A 1TB SSD

6th gen CPU works great with SSD, my 6700HQ is running 500GB M.2 NVME SSD and 1 TB SATA SSD, no idea what prices and availability is in Singapore

Some quick comparison of what "refurbished" Notebooks/Laptops are bringing at TigerDirect Business:
TigerDirect.com | 3WWEBEML2079 | Plus, More Great Deals Inside.

fyi the change doesnt become significant if you have enough ram like if you have 16 gigs of ram once windows load it keeps everything running from ram and hardly use swap and thus an hdd / sshd / ssd become lightly used system wise , as for games / graphic apps load time sshd / ssd gives similar results surprisingly and youtube has alot of videos to prove it and yet ssd is double sshd price .

now a real upgrade would be an optane drive (an intel innovation) , they promise ram like speed with an ssd interface , theoretically is like you just loaded your entire drive in rams so load time becomes flashes , yet however intel sells them in small sizes till date , i think 128 gigs are the highest out there and they sell expensive , so my advice is to go for an sshd and wait on the prices to drop on the optane.

-Edit-
did a little research , intel now achieved a close to a TB capacity for 1200$ smsung evo ssd close to 400$ and segate blazing 2TB sshd firecoda sells for close to a 100$ , so i'd say if that saves you some you can compensate for increasing your ram by something .