I don't know anything about your market target but you would need to lock down your videos if you do not want people to download them.
We do not limit users from views as this only angers those that paid for the service. Using s2Member and Flow Player on Amazon makes it hard for them to download or even see the video file stream. There are many settings you can do to make it so users can't steal your video and share them using s2Member and Amazon. The basics are lock your S3 bucket down so only the user you created for the file access has rights. s2Member handles all the authentications for you and if someone shares a link Amazon will not spool it to the user. If they try to access it from a link in s2Member then your user account will prevent the download and take them to a page you set up letting them know they are not logged in or they do not have access.
I am sure with all the services out there you could find something like YouTube in your market that does the same thing.
Cost, It depends on how much you store on them, your transfers and others. We do not monitor it too closely but every time someone views something they can't download you will pay for it. About 20% of our users re download stuff they have already downloaded, I am guessing because they lost it or are just unorganized. Videos will cost the most and I would think in your industry pretty high. For every 10GBs of data transfer on S3 it is basically a dollar, If you have a 10 minute video at 300MBs and 35 users view it only once expect to pay 1 dollar. If one viewer looks at the 300MB file 35 times expect again 1 dollar. That is for US customers only on S3, Cloudfront is much higher and in the Singapore reign it will be the highest on average. You can however limit your Cloudfront to only a few territories.
It's not free but it is preferred if doing video streaming. You might want to look into content licensing where they download the video to play locally but it is limited to one device.
I am thinking most site like the one you are doing, host from their own servers. I see that almost every hosting company says that it is against hosting that kind of content.