I agree with PurpleFrog, you can always wait for the next promo. On Epicgames, it is $24.99 but check steam, maybe they'll do a sale.
Doubt EGS will be giving away GTA V again for the foreseeable future. However, it really makes sense to add the game to your wishlist on Steam, because the price drop will be immediately notified by email, as Gaben is running a sale quite often.
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Epic games is giving away 1-2 games for free every week for a long time now. If the war between steam and gmepid games continues there might be another hive away. I would recommend checking every month at least once to see the upcoming give aways. There is a big fight for gamers at the moment.