This is a great deal if you value quality
Every time depositphotos comes to AppSumo, there are people who don't read the description: Yes, you buy a one time amount of codes. No, it doesn't replenish every month. How could it? These are high quality files, similar to the big names in stock photos, but for an unbeatable low price.
If you think this price is too high for 100 downloads, then feel free to try to find something comparable elsewhere. I won't wait, because there's none. I've tried other platforms via AppSumo in the past and it's not even close if you care about quality. I've used the "big names" in stock photos, mostly when clients gave me access, and I never miss them.
It's "lifetime", because the codes don't expire as they might do elsewhere. You can fill up your account and use them whenever you want.
What I like about depositphotos besides the general quality of the works is their ever improving website. They've built out the search function and other discovery features a lot over the years. They make it as easy as possible to find the exact right work for your use case.
To be honest: I almost feel bad getting this deal instead of buying it on their site. But, oh well :)