Coating Inner Fork Tubes

Most inner fork tube coating are 500-700 for the set.

No this isnt something you could do yourself, and its a waist of money. It is purely for show, and on a production fork, per the experts like bones bacon at PC, its a performance reduction over the standard chrome finish because it will add material thickness to the tube albeit very little.

TiN and DLC are both similar processes, but have slightly different results. The goal of both is to increase the surface hardness of the tube and reduce friction. TiN is available in a few different colors - turquoise, blue, rainbow, gold, etc. while DLC is only available in black. TiN has reduced friction vs. the stock hard-chrome finish and DLC is even better. The coatings do build up the material thickness, but it is negligibly small at about 0.00014 inches (.0035 mm) and will not affect performance at all.

The coatings certainly increase performance, but it's not a huge benefit. If you're after every last bit of performance available, then they are worth it. But if you haven't had your suspension dialed in for you by a reputable tuner, that would be the first step as it would be far more beneficial than coatings alone. This is certainly not a process you can do yourself as you'll need $500k+ in equipment to do it. TiN is generally a bit cheaper than DLC, but expect $400+ per set of fork tubes to get it done. More if you need everything disassembled.