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QFR is a good solid keyboard, I have one with blacks and still swap it in every now and again.
For PBT keycaps, you won't find many sets below $40. But consider that PBT keycaps should last you for quite a few years, so as long as you get a colourway you like you shouldn't find yourself buying set after set.
Tai Hao sets are usually a bit cheaper, reasonable quality, and sometimes available through Massdrop.