So it seems Habbo.com now offers more credits for your cash, looking like like a fight back against the illegal market. Such a significant update to this hasn't happened since around about 2009 when £3 used to get you 35c (later reduced to 24c).
UK -
Mobile:
20 credits - £1.50
40 credits - £3
HC 1 month - £1.50
Credit card and online:
55 credits - £3.99
110 Credits - £7.49
225 Credits - £15.49
590 Credits - £37.99
HC 1 month - £1.50
To put it in perspective, you used to receive 490c for £50. Now you receive 590c for £37.99, which is 100c more than previous and £12 less.
Unsure about other countries, if anyone does know feel free to add.