There are a number of very good rippers and I'm not against paying for excellent software. I like
dBpoweramp. I'm a PC guy and I'll lash up a bunch of PC's on the network, set dBpoweramp to open the disc tray when a rip is complete, and feed fresh disc's. Early on, there was a fair amount of manual Tag editing, but the databases are much better now. dBpoweramp will display Tags from multiple databases and highlight any differences. One can easily pick and choose on a Tag by Tag level. Artwork fill is reasonable. If dBpoweramp does not present a reasonable artwork choice, I'll briefly search online, then scan the jacket if I don't find what I need. In any case I don't break the rhythm of feeding discs. If there is a problem, I throw that CD on a pile and resolve issues from the pile on a time available basis.
CD reader capability varies and laptops don't have great tolerance for disc defects. I'll give each a disc a brief visual inspection, clean if necessary, and assign the disc to an appropriate reader. I have an old W95 machine that will (slowly) read almost anything -- even discs that cause a real CD player to struggle.
Once I get into the thick of things, I can rip 20-30 discs per hour.
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If you dig around you can find used robotic rippers. For a large one-off project it may be practical to purchase one of these machines and re-sell it after the project is complete.
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I do Tag editing and polishing as a separate step. Note that tag editing is much faster if the library is stored on the PC hosting the editing program. It is several times slower when the library is stored on a NAS drive. If you want the ultimate speed, rip to the individual PC's, not the NAS. This will make scanning the full library while ripping is in progress more difficult. You need to make your own trade-off calculation -- faster ripping or easier management. Once the ripping is complete, merge the library to a single PC, edit the tags, then copy to the NAS. Yes, the copying will require some elapsed time, but you don't need to watch. While the copy is in progress you can tidy up other details, such as sorting and packing the physical discs. Unless the Tag editing is minimal, I think that you'll find that the extra steps will result in less elapsed time for the project.
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By the way, the disc services that I've used will not accept discs in jewel cases. They don't want to waste their time handling each disc. They'll simply transfer a spindle full of discs to their robot. Therefore, either you or the customer will spend a LOT of time extracting discs and loading spindles prior to shipment, then sorting and sticking discs into jewel cases because the discs don't necessarily return in the same order.
