Hmm.. i must say that if you are going to design a character then make it detailed and then have it in 2 different views and that mush the same character that you really can use it as an reference image and in an that good quality so you can see how it is supposed to look like it is about a minimum of 6 hours for each character... but if the character design is going to be realistic you have to make researches about how things work and then make a design from that and then it will take more time... I must say that that prise you said there is low.. Not even worth the time to scan them and send them...
But I can only speak for me… ad a 0 on that MAYBE payment and it should sound interesting...