Hello,
I am new here, just registered to ask.
I have want to buy N900 in India and it is only available on amazon.com and ebay.com

I will be using it for Penetration Testing purposes as its wifi supports promiscuous mode it is great for wardriving and with Kali the possibilities are endless.
What I want to ask is, is it worth to buy Nokia N900 for ~200$ in 2016? or are there any other devices which maybe able to fulfill these roles?
Also from where should I buy Amazon or Ebay or any other place?
I'll also be visiting a 2nd hand device market in Mumbai to find this device.
This is my 1st N900 and I love this device nothing like it has been made till date.

There are no new devices, so all N900's are second-hand.
I'd say the going rate is about 100eur max, no reason to pay 200 unless you get other stuff bundled in and it is absolutely spotless.

Not true. on polish selling sites, like http://www.allegro.pl there are still new unit available for around 400-500 polish zlotys, (around 150 eur).
Even bought one lately and after deeper testing it is legit.

As somtime ago I decided to bought as many as I can let myselft to buy (money), to keep those alive as long as possible. Used n900 cost around 30-50 eur here and the used one n9 from 50 to 100 eur.

Ebay is usually pretty expensive. I think in some countries the N900 didn't sell well and this leads to higher prices on ebay (being a global marketplace).
Based on previous posts about prices I think buying one in Europe, and preferably on a local virtual marketplace is the best approach.
You could ask a member of talk.maemo to buy one locally and ship it to India.
I have never paid more than 30 Euro's for mine and some of them are in excellent condition.

200$ for a N900 i think is way too much. Here in my country N900 is quite rare but still used one's in good and perfect working condition are available for about 50-70$.

I myself have 4 of them. Eying for more if one surfaces for a decent price. There's one for 45€ but it's in other city, thus there might be shipping fee for maybe upto 8 eur.

Just as an update I found and bought an used N900 near me. It is in very good condition except for battery which needs replacement and two cracks between touch & display.

Sadly at september 15th my bag was stolen containing 2 nokia n9, 1 n900, 1 Lg optimus G e970 .

But I never regret when I purchased. If you are curious and want to learn, these devices will provide good experience on it.

So sad. The thief will never sell for its real value...

I just bought another one in reasonable condition for less than 30 Euro. They are becoming increasingly rare for that price though.
Don't really need one but it is nice to have a surplus of N900's