Few instruments allow musicians to transcend the material world. The gourd and wood must be carefully selected and seasoned. Wood thicknesses and instrument proportions must be precise. Proper seating of the frets, fitment of the pegs, and shaping of the surface of the bridge are critical. Even the instrument's polish affects its sound.
Setup is as important as the instrument itself. A decent sitar that is properly set up can sound and play better than a vintage masterpiece that is set up poorly. Sitars purchased directly from India, even from the most respected makers, are about 85% complete when they leave the shop. This is because sitar making and sitar setup require different sets of skills, and few people possess both.
Auction site sitars are called firewood for a reason.
Add some nice carving and decoration, and you've got furniture, not a worthwhile musical instrument.
Don't Risk it.
Think twice about buying an instrument directly from India unless you live there, are an expert in restoration and setup, or are fortunate enough to live close to a qualified craftsman. And you can't rely on your local music store or guitar shop. Chances are, they won't even know how to tune a sitar.
There are only a handful of reputable sitar and surbahar retailers in North America and Europe. It's best to buy from one of them.