Alrighty, I should know this one. I'll give you a ball-park b/c I forgot the exact amount. I'm in the process of getting one once I figure out the colour (from HK).
Medium- HKD $10,400 (really close to this amount)
Large- HKD $11,500 (also close)
I know they are roughly about HKD $1000 apart,b/c I remember saying to my Mom that I'd rather buy the large one if it's only such a small amount difference.
BTW, DON'T fall in love w/the BLUE harlequin, cause they didn't stock it in all of HK Miu Miu. And aparently they aren't called the Harlequin there too.
Hope I was of help! And hope someone else can give you the exact amount!