Here is a compilation of suggestions from my query about door counters:

We just replaced our door counters and ended up going with Trafsys DirectCountTwo. We have about the same number of visitors a day that you have and in the week they've been installed have worked really well! It's a beam counter. That version is able to record traffic in and out by hour, and is downloadable onto a usb drive. I believe they were about $600 a set.

Here's the contact information of the gentleman who helped me with the process:

Jim Fleming
Business Development Manager
Traf-Sys Inc. / Walker Wireless
https://www.trafsys.com/
(P) 412-275-3333
190 INDUSTRY DRIVE | PITTSBURGH, PA 15275
jim@trafsys.com

We went with Sensource. It might be pricy for your situation, but it might be worth getting an estimate.

There are a few listed under "people counters" on the No Reservations Recommendations site - https://nrr.ninja/

We upgraded our door counter right before closing for the shutdown, so we got it set up eventually ;) 

We have always had Sensource, we used to have an interrupter that just counted door opening, but we upgraded to a POE (Power Over Ethernet) counter that has more data on a dashboard to evaluate busier hours as well as just entries. It's probably a little nicer than we need, but it has already been valuable. We have adjusted our hours based on the door counts we were able to track over time. 

We've had one from People Counter for about 10 years. You just have to replace the battery once a year. It sends data to a computer so we can easily see the counts. I don't remember what we paid, but it keeps on ticking!

The Hamburg Township Library has been using SENSOURCE people counter since December 2013.

SenSource, 3890 Oakwood Ave., Youngstown, OH 44515-3033.

Phone: 800-239-1226

The company is very friendly to work with. 

I also just had to replace our 'door' or 'people' counter too. We have a security gate that has both a people counter and the security alarm (for security 'bugs' in library materials). Only the people counter device broke but the material security alarm was still functioning. So, I was able to purchase a device that only counts people for a few hundred dollars vs several thousand dollars for a whole new gate system. Here is what I bought from Demco, in case it helps.

We are a similar size library and we purchased this from Amazon last March:

https://www.amazon.com/gp/product/B0061OP9EG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

It was much cheaper than what we had seen on Demco and we've had no problems thus far. It's very easy to reset each evening. Good luck!