I am only suggesting this because it's what I did, but it might be helpful: You can often find one of the older Cintiq models on eBay for quite cheap.* I got a 15" which only goes up to a resolution of 1024x768 but that's plenty good enough for me, and $400 is a lot more comfortable an investment than $1800 or $2300, especially when I'm only really using it for hobby stuff anyway.
Of course, that doesn't solve the problem of your Macbook not having a monitor port, but ...
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Of course, that doesn't solve the problem of your Macbook not having a monitor port, but ...
*in relative terms, of course