I totally understand your devotion to the Linux platform. You sound like someone that knows how to bring it all together and get the most out of the hardware.
I think I spent $50 on a used windows 8.1 tablet with 10 inch screen on ebay which still qualifies for the free Win10 upgrade. They’re pretty easy to find at that price.The Sainsmart motion controller board that I’m using was $35 but it replaces the mega2560/Ramps combo and I’m using TB6560 3 amp drivers at $4 each and my USB borescope camera was $10 so I’m at about $100 for a full touch screen set-up and that’s including the control board and stepper drivers. The Sainsmart motion controller came with a Mach3 license (legality questionable) so I’m all set. The only drawback is no PWM output for my laser from that motion controller. It does provide a 10v ADC spindle output so I’m working on using an Arduino board to take the 10v analog signal and convert it to 5v PWM (with 10-bit resolution for grayscale improvement). I’m also printing pieces to build a digitizing probe to add on so it’ll be really cool . Don’t know how much I’ll use the probe but building it and figuring it out is the fun part anyway right?