it is possible, but in most cases does not worth it.
Components cost more if sold separately, so usually you end up spending a same amount of money or even more than buying a new bike.
if any seller does discounts on bike - consider you have all the components discounted
planning and implementing conversion is not easy and time consuming
I have done such a conversion on a V-braked suspension fork bicycle. The bicycle had a rather short frame, making the conversion actually end up with a reasonable saddle-to-handlebar distance.
- Drop handlebar + handlebar tape
- Mechanical brake levers with same mechanical advantage as your current levers (for V-brakes, it means long pull; I don't sure what pull ratio your mechanical disk brakes use but I suspect it's the same as for V-brakes)
- 8-speed bar-end shifters -- you won't find these new but you can find new-old-stock (NOS) or used
- New inner cables and cable housing for brakes and gears
- Possibly: a shorter stem
I think such a conversion is a very good idea. The cables, levers and handlebar cost less than a full road bike. If you don't know whether you enjoy road bicycling with a drop handlebar, you'll find out, and you can always go back to your original handlebar. You also have a data point about the frame dimensions in case you decide to stay with drop handlebar bikes, and thus purchase a real road bike. The bar-end shifters are much better than those fragile combined-brake-lever-shifters you find on most road bikes today, unfortunately for buyers of road bikes and fortunately for drop handlebar converters.
Before the drop handlebar conversion, I suggest you to mount some real road tires (such as Continental Grand Prix 5000). Mounting such tires is easier than a drop handlebar and will give you one kilometer per hour of extra speed.
After the conversion, you need to see whether your saddle-to-handlebar distance is good or if you need to mount a shorter stem.