From what I can see on your dates all business fare classes are available, except for J on the return. However, revenue management doesn't need to be about how many seats you have sold but rather about how many seats you expect to sell. As pointed out these are peak travel dates.
With that said, it does seem like TK has raised their ticket prices on this route slightly since the summer.
Results from ExpertFlyer.com (ticket purchased in on June 1st)
Code:
Fare Information Search:
Departing NYC on 24/12/16 for IST
Returning on 01/01/17
Ticketing on 01/06/16
Flying TK
Purchasing at NYC
Viewing in currency USD
Seaching in Business cabin
Validated Results
Fare Basis Airline Booking Trip Type Fare Cabin Effective Expiration Min/Max Advanced
Class Date Date Stay Purchase Req
JYYY3BX TK J Round-Trip 3119.00 (USD) B SU / 8M 50
JY3BX TK J Round-Trip 3699.00 (USD) B SU / 12M 20
JY3BX TK J Round-Trip 4068.00 (USD) B SU / 12M 10
KYYY3BX TK K Round-Trip 4119.00 (USD) B SU / 8M 50
KY3BX TK K Round-Trip 4699.00 (USD) B SU / 12M 20
JY3BX TK J Round-Trip 5068.00 (USD) B SU / 12M
KY3BX TK K Round-Trip 5568.00 (USD) B SU / 12M 10
KY3BX TK K Round-Trip 6068.00 (USD) B SU / 12M
DYRT TK D Round-Trip 7068.00 (USD) B -- / 12M 10
DYRT TK D Round-Trip 7318.00 (USD) B -- / 12M
CYYRT TK C Round-Trip 8254.00 (USD) B SU / 12M
CYRT TK C Round-Trip 9099.00 (USD) B -- / 12M
CIFRT YY C Round-Trip 11466.00 (USD) B
Results from ExpertFlyer.com (ticket purchased on October 14th)
Code:
Fare Information Search:
Departing NYC on 24/12/16 for IST
Returning on 01/01/17
Flying TK
Purchasing at NYC
Viewing in currency USD
Seaching in Business cabin
Validated Results
Fare Basis Airline Booking Trip Type Fare Cabin Effective Expiration Min/Max Advanced
Class Date Date Stay Purchase Req
JY3BX TK J Round-Trip 3599.00 (USD) B SU / 12M 50
JY3BX TK J Round-Trip 3769.00 (USD) B SU / 12M 50
JY3BX TK J Round-Trip 4068.00 (USD) B SU / 12M 10
JY3BX TK J Round-Trip 4238.00 (USD) B SU / 12M 10
KY3BX TK K Round-Trip 4499.00 (USD) B SU / 12M 50
KY3BX TK K Round-Trip 4669.00 (USD) B SU / 12M 50
JY3BX TK J Round-Trip 5068.00 (USD) B SU / 12M
JY3BX TK J Round-Trip 5238.00 (USD) B SU / 12M
KY3BX TK K Round-Trip 5568.00 (USD) B SU / 12M 10
KY3BX TK K Round-Trip 5738.00 (USD) B SU / 12M 10
KY3BX TK K Round-Trip 6068.00 (USD) B SU / 12M
KY3BX TK K Round-Trip 6238.00 (USD) B SU / 12M
DYRT TK D Round-Trip 7068.00 (USD) B -- / 12M 10
DYRT TK D Round-Trip 7238.00 (USD) B -- / 12M 10
DYRT TK D Round-Trip 7318.00 (USD) B -- / 12M
DYRT TK D Round-Trip 7488.00 (USD) B -- / 12M
CYYRT TK C Round-Trip 8254.00 (USD) B SU / 12M
CYYRT TK C Round-Trip 8424.00 (USD) B SU / 12M
CYRT TK C Round-Trip 9099.00 (USD) B -- / 12M
CYRT TK C Round-Trip 9269.00 (USD) B -- / 12M
CIFRT YY C Round-Trip 11466.00 (USD) B