Developing & selling a theme using plugins that have been developed by others

I’m thinking of developing a website to sell themes that I create
(Yes: I know there’s loooads of people doing this already – I just think most people are doing a poor job!)

I just wanted to know what the situation was with bundling ready made plugins?

I would think it a little bit unfair to sell a theme AND use plugins – and not have any proceeds go to the developers of the plugins who have given for free

But then again: I really can’t see a practical fair way round it?

Any feedback would be great

Thanks

Omar