These are two different questions: Improving the language and publication fees. The first is important mainly to make the text understandable. Publication fees are mostly not for checking the language, but for many other expences of the publisher (paying the staff, print costs, taxes, ...). Whether there is a publication fee or not depends on the finance model of the journal in general. Some journals have low costs and sells well or get donations, so they may publish without fees for authors.
I studied in Edinburgh and my English is understandable to any one who read, why do you think I should have someone improve my language? Why would universities give degrees to those who cannot communicate well.
There are higher requirements for publication in a journal than for a master's thesis or doctoral dissertation. It is not just a matter of the text being comprehensible. Since the 19th century, and in some cases even before, good language has been regarded as an expression of scholarship, knowledge and intelligence. For a native speaker with a feeling for language, it is downright torture to read a text with grammatical, orthographical and stylistic errors. Publications in very good language have a much greater chance of being read.
There are two important points here. A group of journals demands for 'publishing operations, taxes, doi payments' etc. charge a "reasonable" fee. The other group is journals called "predatory" that use academic publications for financing. I think it is necessary to distinguish between these two.
Its a valid point , but i dont think , its that serious to worry so much in a scientific writing . I get the same comments even now after putting up 32 years in science. But , it never stopped my any publication in any journal . Non-native english speaking researchers often face this problem , you have rightly said. Usually , editor adds this comment from his side to the papers submitted by non-native english speaking researchers , but i dont know , whether same is applied to those researchers whose mother tongue is english , i simply wonder..??.
We usuallly presume , native english speakers are good researchers as well as good in communicating science , a grossly wrong notion .....
Dear Jigme, i did not respond to next part of your good question about the publication fee. This is your personal decision to choose only those journals who dont charge any publication fee, there are so many high impact factor journals , you can easily choose from . But , there are equally high ranking and high impact factor journals who charge so hevaily as publication fee, its difficult to meet such demand , especially for young researchers. Its an individual take ...for publication
as a non native I had to ask some native English speakers to improve their language as a reviewer several times. - Sometimes we as readers sit and wonder what the authors wanted really to say then it is time for such a comment. - nothing really to worry about just to go through it one more time with the language in focus.
PS I have only made the mistake 2 times in my life to pay fees I think I am healed ;-)