Old thread... but hope this remains as reference for whoever is hiring Gek Jin in the future. 
All I can say is - I'm not impressed with their service and prices. 
My story : bought a 3NG last year and got it this March. 
Well, the place has marble flooring (for living + bed rooms), so I thought to save some $$$, keep the flooring, buang the rest and hire contractors instead of IDs. 
But still, I got quotations from several different contractors and IDs for comparison. 
GJ quoted 25K, and the IDs mostly quoted 30K++ 
So obviously, with a budget, I went for GJ  - which I regret now. 
In general, 25K covered - 
 Hacking - Everything (kitchen, toilets, doors, windows) except for the marble flooring in living + bed rooms2x built-in wardrobesKitchen cabinets, counter topsL-box for 2 bedroomsCornices for living room3 X solid doors, 2 X folding doors, 1 X sliding doorWindows (whole house)Paint workTiling for kitchen + bathroom (up to ceiling)Toilet bowls, sinks, heatersWater pipingGas pipingPolishing the marble flooring
Foolish me should have been more careful with the hidden costs - 
 Electrical rewiring are calculated separateAir-conditioningInstallation of lightingKitchen stoveFittings - mirrors for bathroom, toilet roll holder, curtains, etc...
That, cost me another additional 4.5K. Yes - you HAVE TO BUY YOUR OWN LIGHTS, AIR-CON, STOVE AND FITTINGS. 
So in total, everything turned out close to 30K, just a TAD bit cheaper than the IDs. 
Not the end of story, their communication is abysmal. Worksmanship - depends on their sub-con. 
But you'll have to keep a close eye and crack your whip with them. 
So, if you're not in for a major blood spill, don't save that thousand dollars and just go for an ID.