Corner blocks for the front and back pieces, no need for fancy pocket holes, just get the correct length screws.So the back plate is completely broken - which would not be that hard to fix - but then the front plate has some old water damage and the bolts were ripped out of the sides of the cabinet and so would have to replace both sides. They use that hidden joinery so need some special tools tools to drill those again.
The drawer is fine but the rails are old so would have to just replace those as well. The cost would be a lot less but I still don't have the time to do all this and then if I spend a day or two putting it all together and it's done badly its going to be a complete waste.
Replace runners with new ones
Should be less than R100 in total. Hour max of your time. Quicker if you have a cordless drill.