Most 'plug-in' cards a la PCI went bye bye when the PCI legacy slots went away. Now most people use USB, Thunderbolt, USB/AVB modules. Plus there is a Audio over Ethernet system similar to MOTU AVB called Dante.
Costs are $60-$100/channel with $100/channel being the norm. If the computer has legacy PCI slots there are Delta 1010 and 1010LT cards still on the market. The drivers may or may not be available as M-Audio was purchased in the past couple of years and NO drivers for PCI cards were written with Win 10 in mind.
Cheapest route is at ~$200 for 8 channels analog and 2 SPDIF is the Behringer FCA610 Firewire module. But again the drivers for Win 10 may be an issue.
Thomas