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

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If you just want a basic coffee maker, I’d suggest Bunn. But if you’re just making it for yourself, or need something different, I don’t have a recommendation.
Bunn Speed Brew for the win!
Bunn Rapid Brew, most reliable, consistent and brews a 2 to 10 cups quickly.
I started with an inexpensive Mr Coffee machine, just in case I wasn't going to be a coffee-lovin' exmo. 😆 I graduated to a Bunn Speed Brew coffeemaker with an internal reservoir and love it! I also have a subscription to Lifeboost coffee. It is low acid and easier on my digestive system.
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

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