In reply to acosmin.

Wordpress themes are being sold so cheap there is no real value in them except for some big players (if there was, there would have been no sale). You also need to calculate the time required to master them in order to be able to support and continue development.

For getting the money back you need to calculate profit not revenue. I don't believe the 5k figure is profit as it probably excludes time invested in development and support. Even 100hr/mo in a rate of 50$/hr will bring you to no profit at all. If you can find someone cheaper to do the same work for 30$/hr you get a 2k$/mo profit and you will return the 150k$ in 6 years.

My impression of themeforest is that it is a place for designers of have a dream on a working wordpress themes business, but almost the only ones that make real money over there are evanto which explains the general low quality of themes and support there (ok, been a while since I was forced to buy a theme from there, maybe it had improved in the last two years).