It's not as simple as that, unfortunately.
It depends on how your villa owner is set up - it sounds like they're using a local agent who will be adding your details to the Polis database, which is perfectly acceptable. However, charging over 400tl is not acceptable. For example, Yellali do this service for 600tl for the whole season (no idea how good they are at it by the way!), others do it for 230tl per month including accountants fees (for the tax side of things). Never come across someone wanting over 400tl just to do one booking.
Sounds like someone is making a lot of money for little effort, and it also just crossed my mind that it may not be entirely legal to do it this way, i.e. charging guests a fee directly to be entered on the Polis system. Inspector may be able to shed more light on that aspect.
JF