I sell traffic so i might sound a bit biased but the truth is, it can convert for some but not everybody
I get a lot of people who buy traffic expecting it to convert and if it doesn't they threaten to leave negative feedback in return. What you have to do is picture yourself as the visitor, all the traffic I sell is pop under so in order to keep the visitor interested the page must look nice and professional and be related, not some poor looking squeeze page that's barely related to the user, it has to be something they are passionate about
good example - you run a golf e-store and buy some golf related traffic, the visitor will most likely be on a golf news site and he goes to leave he notices your site is open, its a nice looking landing page with some great deals on well known brands, maybe even has a verified by visa/paypal badge and HTTPS - the chance of this visitor converting is HIGH
Like I said tho its hit and miss, this year about 40% to 45% of my clients reorder so that paints a picture on the percentage of people who can get this traffic to convert