There seems to be some conflation between relevance of:
1) GDP (nominal, USD , current)
2) GDP (nominal, USD, constant)
3) GDP (PPP, USD "international", current/constant)
w.r.t their applicability for things like production, consumption, industry and so on....all the way down to specific project like say space launcher development or aircraft carrier acquisition between say country A and country B.
Each of (1,2,3) all have their individual merit and weakness for such comparison, scope of which will take too long to get into the required depth for every economic sector.
Suffice to say the specific relevance (of harnessing optimal opportunity cost and scarcity of resources i.e the very definition/objective of Economics) depends on the foreign reliance (for supply) of something versus local provision (for supply) of something....in % terms of everything that goes into (the subject matter at question).
If a country has certain number of trained professionals and resources that are organised over long time to develop and deliver a certain product and largely localised in supply chains and component creation, it is not really a question of strict GDP USD nominal applying to this....or even PPP with argument that "labour is cheaper" as though these people involved in such sector consume and live less and are "cheaper" to hire than their counterparts in some more USD-flush and USD-integrated country.
That is not how it works at all I am afraid....it is more a case of opportunity cost for such sectors relative to others...largely using the local currency budgeting and other scarcity metrics.
India simply put in the hard work right from the 1970s to develop a certain space launch capability because it knew it needed it for both military and civilian application.
It was not made with the intent to trade on open market, that is just added benefit that came with time in the market place of a globalised integrated competitive world.
Just like if you initially invested a lot into your population's education and training for doing specific things in closed economy, once the economy opens....it will get better USD (world) referencing naturally over time. India is in process of doing this still given its size, so its not really optimal to compare lower tier bulk macro economy references to spearhead tiers of innovation (like space, defence, nuclear etc) until the macro economy is more saturated/integrated with world supply chains....i.e more "developed".
i.e foreign launch marketing makes a tiny portion of ISRO operation and budget (USD liquidity by direct trade with others). USD trade w.r.t Indian economy is still quite small too compared to Indian economy on top. But the results of each ISRO launch is there to see....i.e the qualitative referencing. This is all what leads to Indian launch being "cheap" due to surplus rupees w.r.t USD need in other parts of the economy....that influence the exchange rate far far more.
So it is faulty to apply (1) and say Indian labour is "cheap" as though such labour in this field is so easily developed and easily flexible to compare on basis of millions and billions of other regular transactions/trades of far more mundane nature.
In that respect (2) and (3) would be better reference points ....as indexed inflation is far more domineering on Indian local price levels than exchange rate (esp for fairly non-exchange rate reliant activity)...but they are still far from ideal for this purpose.
Similarly for Turkey, for an aircraft carrier project....you cannot simply look at (1) and say automatically its too low to achieve it.
It would depend how much of the aircraft carrier comes from internal Turkish know-how, resources and labour (and the opportunity cost of deploying it here compared to another development).
If a large part of it needs to be imported or needs import flow then (1) becomes dominant.
If a large part of it can be done locally and does not need much import flow then (2) and (3) become more dominant reference points.
Then of course you have to look at further opportunity cost past just GDP (an overrated macro measure that is not highly relevant for individual projects)...things like fiscal buffer, govt budget, raw technical manpower availability, specific capacities (i.e in this case no. of shipyard spaces and existing committed order book etc).
I am not a Turkish Navy planner, but I at first glance at Turkish navy current profile would rather go for far more frigates and submarines before even LHD/LPD (and I would use all my local shipyard capacity to Rnd these 2 and just buy a LHD or two if I really need that).
Critical capacity use must always always always be looked at as a great opportunity cost past just the budget itself....as if you tie up a shipyard space (time-wise) for a LPD for say same final price/final time as 2 frigates....but the 2 frigates gives you 2 - 3 times of the relevant power level you need to project....it is best to use the local shipyards for the latter as priority and 2nd priority would be LPD/LHD (and maybe look at import if you really need it as well). Cost of setting up new shipyard and training workforces also comes into all these equations.
I would avoid aircraft carrier altogether till cpl decades down road....till Turkey internal finances are much more robust. Again this has little to do with nominal USD GDP if the know how and resource is already within Turkey (And if it need lot of importing, then USD GDP definitely factors in as it would be trade that needs to go through it, as Lira needs to be converted to USD for this effectively).
But if knowhow + capacity is localised + available for argument sake... it is more case of govt budget/fiscal pressure (in local Turkish Lira) and opportunity cost w.r.t production of other kinds of ships for Turkish Navy at those shipyards instead.
It would need a sound reading of Turkish naval strategy till 2050 I suppose. That is not something I know much about.