Mate, there's YouTube "benchmarks" of GTA V that show the GTX 480 doing constant 60FPS at 1080p max settings. The only YouTube videos you can reference if you want any credibility are those from large YouTube review channels. The GTX 980M can't do more than 30FPS with triple-A games at 4K (at decent settings). If you want to prove otherwise, do a live benchmark with your laptop and then maybe anyone will believe you.
There's no "cheaper solutions" that aren't in the GTX 1000-series. The card you want for 4K is the GTX 1080. If you can't afford that the next best option is the GTX 1070 which still outperforms the 980 Ti. Older cards simply can't compete.