That you're still making this argument just demonstrates an over-reliance on sparse dictionary entries that do not squarely address this issue.
There is absolutely no question about the fact that, in modern Irish, when you are referring to the price of something, saor means "cheap", an-saor means "very cheap", níos saoire means "cheaper", and is saoire means "cheapest". You do both yourself, and other learners, a disservice by continuing to insist that saor means "free" in the context of price.
There really is an important distinction between "free" in the sense of "liberty" and "free" in the sense of "zero cost", and it's misleading, and probably even béarlachas to insist that saor should be interpreted as "free" when the context is cost.
(This is a reply to Knocksedan; I’m replying here because the comment that I’m replying to doesn’t have a Reply link.)
Words can have more than one meaning; for example, “cheap” can mean either “inexpensive” or “shoddy”. Similarly, saor can mean either “inexpensive” or “gratis”, as the dictionary entries that were cited in the other discussion show. I have no reason to doubt that saor has a primary meaning of “inexpensive” in modern Irish regarding prices; however, that primary meaning does not exclude the validity of other meanings.
I am not insisting that saor means “gratis”; I am insisting that saor can mean “gratis”.
Regarding its origins, saor has had a “gratis” meaning since Classical Modern Irish (see definition (f) here); given its time frame, it’s certainly possible that that meaning came from English. Looking at definitions (a) through (e) there, it seems as though the “inexpensive” meaning came from the “easily obtained” meaning of definition (f). Since they’re both part of a single definition, if the “gratis” meaning came from English (as opposed to being a particular case of “easily obtained”), then perhaps the “easily obtained” meaning did as well.
EDIT: Among the many definitions of “free” in the OED are A. 22. c.,
Unstinted as to supply, quantity, etc.; coming forth in profusion; administered without stint; abundant, copious.
which seems to be the closest definition to “easily obtained”, and C. b.,
Without cost or payment. Often with gratis added, esp. in colloq. phr. free, gratis, (and) for nothing.
The earliest noted written use of the former was from 1635, and (apart from the phrase “scot free”) the earliest noted written use of the latter was from 1682.
Interestingly, the eDIL sources noted for definition (f) above are poetic works. Since Classical Modern Irish lasted from the 13th through 18th centuries, those poems would have had to have been composed in the 17th or 18th centuries for English “free” to have possibly been the source of the definition (f) meanings. If your local library has copies of the Dioghluim Dána and the Aithdhioghluim Dána (both edited by Rev. Lambert McKenna, S.J.), then perhaps information could be found in those books on when those cited poems were written.
"inexpensive" is a slightly formal synonym for one of the meanings of "cheap". saor can also be used for the "low quaility" meaning of "cheap", whereas neamhchostasach/"inexpensive" doesn't have that meaning.
But in this case, "inexpensive" isn't an unreasonable translation, just a slightly less common one that presumably didn't get added as an acceptable alternative answer.