I saw someone selling 3 spots to fashion advertisers on a site that gets 600 reads per week. The cost was $25 per spot. The first reply was misspelled and crudely suggested that the site was too small. I think that response is highly stupid. What if the 600 readers dwelled on the site and they were monied and looking to buy? What if the advert was attractive and the product and service was too? In magazine advertising I'd say that a 5% response is high but attainable if the advert/product is attractive. Reproduced the 600 would give a 30 response and if each sale made $10 that is $300 and well worth the $25 paid for the spot. Eventually advertising executives will come to understand and that's when quality sites receiving 500+ readers will be of interest to them. People who can recognise online space that appeals to readers with expendable income and match that with what they are buying will be worth their weight in gold. What good are 2 million readers with no money?
The conversion rate really depends on your LP, your sales copy and how you present yourself. The marketing is already planned out.
Of course a high volume of traffic whose population has considerable expendable income is desired. Putting an attractive product in front of it in an enticing manner is also (should be) a non-brainer. However, when I see some of the crap purporting to attract such an audience and service in the manner indicated it is obvious that there's an abundance of deluded web masters and marketers online. Concomitant with these delusions is the inability to stage debate.
I think the best traffic is the one that convert to sales. You can have high traffic that does not convert well and sometimes, very low, quality traffic that convert. In the end the best traffic is determined by conversion rate.
if you're looking forward for more sales or leads, choose quality traffic. quality traffic can give you targeted leads and sales.