You can get networked multi-function printers (MFPs) with an automatic document feeder (ADF) and duplex that scan to email or a network share for already 200-300 $. But their scanning speed is rather slow and the workflow is not automated enough (according to my experience with MFPs from Canon). A much better workflow offer networked MFPs that allow to configure your own scan profiles on the MFP (but you probably will not get one below 3.000 $). For scans you put a pile of documents in the ADF and chose a scan profile and the MFP hopefully does the rest. Hopefully because double feeds and paper jams happen or you need searchable PDFs in a language that the MFP does not offer, ...
To avoid double feeds go for a scanner with Ultrasonic Double Feed Detection.
If you scan documents that are not completely flat (e.g. invoices that were folded or purchase orders that caught a few raindrops) it happens that the resulting scanned image appears slightly blurred in some parts of the page. If you need searchable PDFs of your scanned documents this will cause problems for the OCR software. The OCR software might not recognize the blurred areas as text/figures. As a consequence you end up with a PDF were only parts are searchable (or can be copied and pasted e.g. into an accounting software) while other parts (that might contain relevant information) are not. To avoid this, you need a scanner with CCD elements instead of CIS. This is because CCD has a much wider depth of field than CIS, so that blurred areas are avoided with uneven paper. I have a Canon ScanFront 300P network scanner with CIS and these blurred areas that cannot be copied and pasted from PDFs are a pain. The Kodak Scan Station 500 has CCD as well as the Fujitsu fi-6010N. Appart from that the Canon ScanFront 300P is user friendly and offers an easy workflow with its touch screen and configurable scan profiles but it is too slow for my taste (speed according to specs: simplex 25ppm in color at 200/300 dpi, duplex 40 ipm). Such and similar network scanners cost at least 1.500 $ or even twice that. So don't expect to get a MFP below 1.500 € with acceptable scan speed, image quality, and user friendly/automated workflow (apart from reasonable printing speed, ....). You rather need to be prepared for 3.000 $ upwards.
In a business environment higher scan speeds are advisable. Manufacturers usually give the scan speed at 200 or 300 dpi. But some documents might need 400 dpi or even 600 dpi (if they contain very small print that needs to be readable by OCR software for seachable PDFs). Many document scanners slow down considerably at 400 dpi or more. Some slow down when you want to get color images from your scans instead of black and white or greyscale ones. Color information can be important, e.g. if there are colored notes or parts marked with highlighter (they might completely disappear in a greyscale or b/w image). So check the technical specifications for scan speed in color before you buy. If the specs are 25 pages per minute in color for 200 or 300 dpi (in simplex mode, and 50 images per minute in duplex) it's highly likely you get perhaps 12 pages per minute in color at 400 or 600 dpi (simplex and 24 ipm in duplex). In a business environment I find this too slow. In order to have some margin for higher resolution scans I would look for a document scanner with at least 30 or better more pages per minute in color (simplex, and 60 ipm duplex).
I do not recommend to buy a consumer grade MFP for your purpose. You will not reach your goal of automated scans at a reasonable speed with such hardware and software. Instead, you will loose a lot of time fiddling around with such equipment. 1.500 € or even 3.000 € is a lot for a small business, but from my own experience that is what you need to spend to get close to your goal.