I think this would be the best possible English translation.

Living can be replaced by wages.

The wages of righteous means of living is manifest worship.

You can replace precise in the Target Term above by manifest.

یہ ترجمہ مشہور و معروف ہے اور پاکستان کے ہر کرنسی نوٹ پر لکھا ہوتا ہے۔

بعض لوگ یوں بھی اسے ترجمہ کرتے ہیں

Honest livelihood is equal to prayer

The is is 100% true that "Acquiring lawful earning is a form of true worship".

--------------------------------------------------
Note added at 3 hrs (2017-07-19 07:33:37 GMT)
--------------------------------------------------

Earning a just income is exactly the divine worship.

--------------------------------------------------
Note added at 1 day1 hr (2017-07-20 05:31:10 GMT)
--------------------------------------------------

Earning a Halal income is exactly the divine worship

To put it differently...

I'm offering alternatives after reading asker's entry in discussion, to bring translation closer to its Islamic meaning. The other translation I offered is a general one that can be understood by non-Muslims as well. "Righteous" implies God fearing, and describes "halaal" better than "honest" which is also a secular concept.

"Sustenance" can encompass other types of رزق than just an earning/livelihood.

Other suggestions:
To acquire sustenance by righteous means is truly an act of worship
To gain sustenance righteously is truly an act of worship

The word عین is not an adjective for "worship". It's being used as an adverb.

Some other ways to translate the same more literally would be:

"Earning honest living is truly an act of worship"
"Earning honest living is precisely an act of worship"

But the essence of the phrase is better conveyed the simpler target translation:
"Earning honest living is an act of worship"

--------------------------------------------------
Note added at 20 hrs (2017-07-20 01:07:02 GMT)
--------------------------------------------------

Thought of this alternative later; I prefer this:

Earning honest living is an act of worship

--------------------------------------------------
Note added at 2 days5 mins (2017-07-21 04:32:17 GMT)
--------------------------------------------------

The comment section below does not allow me to reply properly, so I will do that here. Just because the word عین is next to عبادت does not mean it is describing عبادت.

Moazzam sahib, in the explanatory translation you gave below quoting ہوبہو ، بعینہ، both those terms as well as عین would fit exactly where you used "is nothing else but"...that is the place for all these adverbs. That is why I used it as "truly" which means exactly what you translated as "nothing else but"...but that is where its usage ends.

You cannot extend usage of عین as an adjective by attaching it to the noun "worship" by translating it as "true worship". That changes the meaning of the sentence by giving it a very different connotation. It then implies that earning honest living is "true worship", as oppose to other forms of worship that we commonly associate with acts of worship like salat, fasting, zakat etc. That is not what is meant. It just means, earning halaal living is also an act of worship. The significance lies in the fact that earning a living is not generally taken as worship.