It's not that simple. You'll want to look at GDP/capita to compare countries in general.
My point is a different one though: If Turkey joined the EU, it wouldn't be a net contributor, it would get huge subsidies from the EU. As such, it wouldn't benefit the EU economically, and it would be a disaster politically. It may be nice for some private companies to get easier access to a new market, but the price would be much too high, and I'm fairly certain that the EU would not survive Turkey as a member state.
My point is a different one though: If Turkey joined the EU, it wouldn't be a net contributor, it would get huge subsidies from the EU. As such, it wouldn't benefit the EU economically, and it would be a disaster politically. It may be nice for some private companies to get easier access to a new market, but the price would be much too high, and I'm fairly certain that the EU would not survive Turkey as a member state.