As they are unregistered and unhealth tested ethically you should only charge what they cost you to raise. You have no proof they are pureBRED, and if they are different sizes even though they are the same 'breed' mixing sizes still makes them mutts.
So cost of vaccinations, food, worming etc. You are probably looking at around $200 per puppy. Anything else is just being greedy if you haven't done the leg work before breeding.
Registered, health tested dogs sell for thousands simply because they have cost the breeder thousands to have all their testing done, then you have certification in working trials, agility, obedience and conformation... it all costs.
If you desex before sale you could charge up to $500.