Not colocated, but in the US, you can find a dual EPYC 7742 (64 cores) with 512GB of ram (with ssds, hdds, and bandwidth included) for $1000/m.
This should absolutely demolish the c5.12xlarge, especially if you need any disk IO or bandwidth.
Or from a different provider, a Dual Epyc 7281 (32 cores) with 256GB (and ssds, hdds and bandwith included) for $400/m.
You can get cheaper if you're willing to host in Europe. And this is dedicated, so no additional power or storage or maintenance cost. Stuff breaks, they replace it. Also, your commitment is 1 month.
To add context to the downvotes you've acquired: I didn't downvote you, but I think I understand why others did. Your parent comment was asking about 96 GB of RAM, and you posted a reply talking about 512 RAM. I suspect others thought you were talking about 512 MB (ie. 0.5 GB of RAM, which is common in very cheap hosting) rather than the 512 GB of RAM you actually commented on. When I first read your comment, I admit I first saw "512 MB", but you quite clearly wrote "512 GB".
tldr; The number "512" when talked about in the context of RAM is assumed to be measured in MB, but 512 GB is also a less-commonly-encountered amount of RAM. :)
This should absolutely demolish the c5.12xlarge, especially if you need any disk IO or bandwidth.
Or from a different provider, a Dual Epyc 7281 (32 cores) with 256GB (and ssds, hdds and bandwith included) for $400/m.
You can get cheaper if you're willing to host in Europe. And this is dedicated, so no additional power or storage or maintenance cost. Stuff breaks, they replace it. Also, your commitment is 1 month.