First lets talk specs,
i7-7500U has 2 cores with hyper-threading, 2.7Ghz boost to 3.5Ghz with 4MB cache (arch:14nm, date: Q3'16)
i5-2300 has 4 cores with no hyper-threading, 2.8Ghz boost to 3.1Ghz with 6MB cache (arch: 32nm, date: Q1'11)
Performance:
Even that the old i5 has 4 physical cores its old architecture could make it lack behind a logical 4 cores (2 cores with HT)
Checking the single core performance, the i7 gets 1,957 points and i5 gets 1,571 points
As for the all cores performance the i7 gets 5257 points where the i5 gets 5280, almost the same!
https://www.cpubenchmark.net/CPU_mega_page.html
Pricing:
the price listed at Intel site for the i7 is the suggested price of the CPU when they sell it to Notebook manufacturers, it is expensive yeah because its a 15Watt high end CPU and as you can see it managed to match a full 4 physical cores of the i5-2300 which has a 95Watt TDP!
Conclusion: I think it will perform on par of the i5-2300 in games, considering it is the minimum required CPU to play the game it means it will - combined with the 940MX - give you 50fps average in H1Z1 720p low
Check this video, he is using i5-6200U, so with your i7 and the boosted 940MX you should have better performance
https://youtu.be//8vz4mg6-Mms