
Moccamaster (Technivorm)
KB Series
Durable, repairable workhorse, but pricey with basic features.

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I second that. I’m using a Bunn thermal carafe. It produces consistent hot water and is always ready. The brewed coffee stays hot for several hours. I bought it over 5 years ago and use only filtered water so no scale build up. Now when it dies I will replace it with a Moccamaster thermal carafe.
In your situation, I’d ask for a Bunn 10 cup home coffee brewer. It’s the longest lasting, most reliable, kitchen appliance I’ve ever owned. Nothing beats it. They have fancier models, but the one I mentioned is the one I have-have had for years.
If each of the 20 drinks say, a 12oz portion that's 240oz or 30 cups. So you're looking at 3-4 runs with a 10 cup machine. Machine: Bunn. There's 10 cup options around $130. Carafe: Whatever. You can get insulated carafes for like, $20-$30. This will help your production line since you can't fit a commercial Bunn in that budget, keep one of those full + the pot. Grinder: You can get an OXO for $80-$100, or a Cuisinart for $50. Cuisinart grinder + Bunn 10 cup + cheapo carafe keeps you in budget and should all work great. Splurge on nicer grinder if you find more coin, Baratza Encore. Or go even cheaper + showy (though more difficult/more time) and do boilers and pour overs or french press made to order. Spend more on the grinder if you go this route.
I like one of the Bunn home brewer models. My only complaint is they are shipped with a plastic funnel
I've always had BUNN pots, but the quality on the residential ones has gone to crap, a few years ago, I splurged and bought a commercial grade one that plumbs directly into the water supply! The hot water tap is nice for my wife who loves hot tea and the kids for cider or cocoa.
IMO nothing beats a restaurant Bunn or one of their clones. Water is always hot, brew as much or little as you want, if you replace the plastic basket with stainless you have zero plastic from the boiler to your pot. The only better coffee IMO is pourover, Bunns are like pourover for people who don't want to fuss over their pot.
Yes, they're not cheap. Buy once cry once they are BIFL

Moccamaster (Technivorm)
KB Series
Durable, repairable workhorse, but pricey with basic features.

Moccamaster (Technivorm)
CD Series
Built to last, brews great coffee, lacks timer, expensive.

Moccamaster (Technivorm)
Cup-One
Single-cup, built to last, excellent coffee, but pricey.

Moccamaster (Technivorm)
GCS
Durable, SCA-certified coffee, but pricey with uneven water flow.

Fellow
Aiden Precision Coffee Maker
App-controlled customization, but unreliable and finicky interface.

Ranked #1
Fellow - Aiden Precision Coffee Maker

Ranked #1
Moccamaster (Technivorm) - KB Series

Ranked #1
Moccamaster (Technivorm) - KB Series

Ranked #1
Moccamaster (Technivorm) - KB Series

Ranked #1
Breville - Precision Brewer Thermal Carafe

Ranked #1
Simply Good Coffee - SimplyGood Coffee Thermal Brewer, 8-cup