Over the last 15 years they have been, they may not be top 10 at this moment but overall they are when you take into account overall growth over a few year period. In the mid part of last decade they were the fastest growing economy in the world. They are also now classed by the world bank as a high-income economy, it's hard to keep up rates of growth as a percentage when you are taking a percentage of a higher total. They have more than doubled the average wage in 15 years.
The point is that they are a very real success story, and it's forseable that several of these countries - including Slovenia and Estonia will contribute back more than they take from the EU very soon.