my most expensive board would be my k70. buying keyboards here in Singapore will drive you bananas, as there is only one place you can go to for quality boards. i reckon there are over 50 singaporeans here on geekhack (( that are active ofc ))
i paid around 150 usd for it, although it came with a cm mousepad that is foc.
what drove me to buy this keyboard is not the free mousepad, but the features this board offered
a volume wheel, dedicated media keys, backlighting, custom backlit area selection, bios, usb pass through, 1000hz polling.
i thought these were essential features i would use often, and i loved the black body and red led colour scheme. thus, i felt like it was a end game board for me (please don't laugh at me). it was also available in my favourite switch type; reds. this all happened before i chanced upon geekhack and i had no idea that 6.5x spacebars is near impossible to find.
however, what drove me to buy this board is still what keeps me from selling this board away without reluctance.