We have a Mayan-EDMS appliance. You can download it for free and run it in a VM if you wish. But I'm guessing from your question, that you want it hosted. E.g. via the TurnKey Hub?!

If so, then it will depend on how much you want to spend vs the performance that you need/want. The Mayan docs recommend 4GB RAM, 2GB as a minimum. That suggests that you would at least need to run it on a t2.small (1x vCPU; 2GB RAM), or preferably a t2.medium (2x vCPU; 4GB RAM). If you plan to use OCR, then you may even want a larger one?

To run small or medium servers from the Hub requires a "Cloud Bronze" plan (@$20/mth). The AWS usage fees are variable and depend on a range of factors, including which region they are running in. It's also worth noting that there is a cost per GB/mth for the storage volume too (aka EBS - elastic block storage). Currently that is $0.08/GB/mth - so $1.60/mth for a 20GB volume; $8.00/mth for 100GB. However, it should be noted that you could save yourself some space by using AWS S3 storage for your docs (which is about half the price of EBS). You still need a EBS volume for the OS, but you won't need a big one to store all your documents. (Please note that I have no experience with setting up S3 storage with Mayan, but if you use the Hub, I would be willing to provide "best effort" support to set it up).

Whilst they are variable, let's do some rough back of the envelope figures. Firstly it's worth noting that while you are initially testing, you'll want to just pay the "on-demand" prices. Once you are happy with the performance of your server, then you can reduce your AWS usage fees by purchasing a "Reserved Instance" (sort of like a pre-paid discount). Depending on a range of factors, the discount may be as much as 40% off AWS usage fees.

The AWS pricing pages aren't organised that well, so here's a 3rd party interactive table that makes it a bit easier. So the rough monthly cost for a on demand t2.small will be $15.45/mth (~$9.70/mth reserved. The rough monthly cost for a on demand t2.medium will be ~$31.20/mth (~$19.30/mth reserved). Plus the EBS volume & S3 doc storage costs. It's also worth noting that network traffic in is free, but traffic out over 1GB/mth will attract additional charges...

I hope that helps a bit?!