There's a.... rule about pricing yourself for creating artwork. You can ask any professional artist or sculptor or anyone that creates fine-art for a living but not necessarily with any direct connection to entertainment industry sectors such as pop music, silver-screen cinema, advertising, glossy magazines etc.,... Anyways the rule goes like this:
When you get a certain nominal to do artwork, and it seems that you're getting priced somewhat above your [perceived personal] worth, you don't tell your client that s/he's over-paying you, instead you say thank you and feel honored. And going forward, make sure the quality of your art continues to improve to match your offering prices.
Some artists may add some qualifiers such as, if you're getting offered way, way above your normal prices, something like Orders of Magnitude (10x, 20x, 100x), then you should at least question your client's wisdom at least once (or maybe twice if we're feeling generous); and if the Client continues to insist, then you accept the pay. And then the Artist follows the rest of the above rule. But these are personal preferences I think, subjective and still up for judgment etc.,...
What prompted me to write this is that recently one of my graphic design works got offered for about 5x what I normally (expect to) get paid for; and this after just a few weeks before my artwork was paid twice what I normally (expect to) get offered. I never stated a starting asking price, and I accepted what I was offered without question. This of course places upon me the responsibility of increasing the quality of my digital artworks to match my "fee grade"/"pay grade", and it's a challenge that I intend to face head-on.
There's also another rule that goes, "Always work for cheap, never work for free," but I think I'm going to save that for my next post hehe