Yes, 'tis is "it is," a humorous echo of eighteenth-century speech.
My questions were not about the correctness, but the implications of the language. What didn't fit, for me, was the "I" in what I assumed was a formal document or letter to the recipient of the salary. If the decision has been made, and the writer has the power to decree what currency the salary will be paid in, is he inviting disagreement by implying that the decision is only his "preference?" If it is still to be decided, and the recipient may make a counter-proposal, then why not say that?
So, assuming it has been decided, an American letter would simply say, The salary will be paid in [US?] dollars. (This is probably a matter beyond translation per se, and if so, sorry to intrude it!)
A family member pointed out to me that "on the basis of a currency" is not the same as "in a currency." (I don't want to mislead you!)
So, if the Labor Agreement has not been drawn up yet, and this is a negotiation, then let your main idea stand. (If "I" represents a company, you might replace the pronoun with the words "The Company," or "We.")
In the Labor Agreement, the Company prefers to establish the dollar as the currency basis of the salary.