They can charge whatever they want, the idea that the game is two years gone on console ergo it should be cheaper once it reaches PC is quite comical though. The conversion quality and content vs the delay should determine the cost not how long it took to get here by itself.
What I can say is that having paid full price for PS3 and PS4 versions once the single player is done the majority of the content switches to the online portion and Rockstar have fooled me twice with that one. The online gameplay is an example of one step forward nineteen yards backwards but whatever the case Rockstar have had two years to get the online infrastructure sorted, to stream line the service and make it a smooth and enjoyable experience and to this date it is lacking basic functionality and service which should have been there right from the start. Actually doing anything outwith freeroam ends up taking way too long and feels like a chore rather than a fun gaming experience.
The thing is though the basics for an outstanding experience are there, if Rockstar pulled it's head out of it's arse and spent just one or two updates actually fixing the issues (crappy servers support, piss poor matchmaking, the constant jumping from host to host, the fact that EVERY mission has to be downloaded at join, get rid of the armoured vehicles don't fucking add more) instead of launching wave after wave of Shark Card selling content updates the online part of the game could be truly outstanding, The Heists gave us a small look at how good it can be.
The problem though is
a). I see no way in which the PC release is going to improve things, in fact I am willing to bet that not only will PC players have issues playing online on release but so will console players.
b). With the heists out and the PC version out say good bye to the free shark card selling DLC and say hello to the paid for DLC.
To put it simply Rockstar couldn't get me to pay for another version of GTA5, even the ability to mod the game won't draw me to pay for the PC version, though I suspect the modding community is going to be disappointed with just how locked down the PC version will be.