Kimsufi was launched to fight against french Dedibox (now online.net), which at the time had lower price than the lowest OVH server. They stayed at the same level as them since then.

Could that be due to differences in VAT?

If not it might just be that they like to quote nice round figures (£14.99 and €14.99 perhaps) - this happens sometimes when the pound and the euro are (or recently have been) near parity.