I used IndiaMart and have bought off 2 different sellers using Paypal each time. It's great to be able to use Paypal but they can't list what you are buying for obvious reasons so there's a big risk there.
The last seller gave a great price but took forever to send it, probably because I was specific about which brands and strength I wanted so they had to source it but it was 2 weeks before they sent it. They[he] bluffed me saying it had been sent and I contacted Indiamart to complain. They were quick to respond and clearly did not want customers to have any problems with sellers but before I started any formal process he sent it off and gave me tracking.
I think they expect you to barter so don't be afraid to ask if they would do the deal for a lower price. At the end of the day they are trying to make a living and want repeat business and referrals. All of the conversations with the seller are recorded on the Indiamart site so that it's transparent if there is a problem.
