This computer sells for about $100.00 as configured, but then with a few upgrades you could do to get a bit more life out of it.
RAM: This Dell Inspiron ships with 6GB of RAM but you can max out the ram to 16GB. For this computer I wonder if adding ram that costs more than the computer is such a good idea. You could upgrade to 8GB but as it ships with 6GB you would be hard pressed to tell much of a difference
Hard Drive: This is different. This computer ships with a 500GB drive, but I suggest you toss a SSD in this computer. You could get away with a 128GB ssd which would cost $100 or less.
Battery: This computer could probably use a new battery and these are pretty cheap at about $20.00
Total Cost of Dell Inspiron 15-3521 with Upgrades would cost about $220.00