Being offered $250, shipped, for a snake advertised at $350, shipped isn't all that horrible, once you've been doing this for a while. Don't get me wrong - it's nearly a 30% reduction, and I would decline the offer...but I get offered prices that are 40-60% less than my asking price too frequently (and I don't inflate my prices to allow for negotiation).
I do understand your point; but when you break down the offer like that in an attempt to show how bad it is, well....crap, I don't know how to put it. Look at it this way. You broke that offer down to $170-180 - which on the face of things looks pretty bad for a $350 asking price. However, break your asking price down the same way, with the same shipping, and a slightly higher paypal fee - say $10-12 (you overestimated, so I went with comparable numbers) - your asking price is only $270-280. (The net result is the same as before the breakdown...I think your displeasure with the offer just drove you to see it in the worst light)
I'll admit that I'm not aware of "current" or "market" pricing on mojave females; BUT, at 200g, she's still a baby - not really to the point where you would expect to get more money for her. It's nice in theory, but that isn't how it works. You might be basing some of your thoughts on the erroneous belief that subadults and adults actually sell for some of the crazy prices you see posted. A few might, especially if there is something extra nice about them, but most will get knocked down hard if the seller wants them to move.
Dealing with pricing is tough. You can spend weeks researching advertised prices before you post your animals, and go in at what you think is fair based on what you have seen...but how accurate a reflection does that give you? I could look at the classifieds right now and say that a 1400-1800g female pied sells for $3000, because I've seen several posted at that price...but, the simple fact is that those same animals have been up for a month, and I doubt the sellers have been offered anything close. THEN, especially with current year babies, there is the degree of competition. IMO, your asking price is probably toward the high end for mojave females at this time. Does that mean you shouldn't ask that price? No. Absolutely not. But be aware that other people are posting females as low as $225 shipped (I just looked). The norm seems to be closer to 275-300 shipped. Of course, once you review all the prices, and post your animals at what you feel is a competitive price, somebody is going to come along and post lower prices because they want to sell their animals and lower pricing gets attention. It's sad, in a way; but for a large part of the customer base, price is the factor that drives a sale. The percentage of people that have specific wants, and are willing to pay more for them is disappointingly small.
Shipping is another issue. You are in a similar position to me, geographically - we're at opposite ends of the country, but we're both in areas that put us at a good distance from many of our potential customers. You might want to look at SYR, to see if you can reduce your shipping rates - or maybe you can use a smaller box size - because if you're looking at $70 to ship a baby BP, you aren't being competitive. It sucks to say it, but you might have to eat a little of that if you want to move your animals - whether you consider it lowering the bottom line on your animals, or not breaking even on shipping (which can be hard to do - I've had people try to charge me $20 for the box, on top of shipping, because that's what it cost them to get the shipping box (including its shipping cost). I've also had people try to charge me $100 for shipping...and when I checked, I found I could ship an appropriate sized box to them for $65).
It is people like this that ruin our hobby. If you can't afford close to the asking price, be respectful and just don't respond. It is insulting and irritating as heck!! We work hard to breed, feed, and maintain our snakes and a low-ball offer is the ultimate insult. Often it seems to be the newbies who feel it necessary to low-ball. They obviously haven't taken the time to raise and care for a snake and have not learned just how much time, love, and attention it has taken to get the snake to where it is. I really wish the "buy cheap, sell cheap" people would just go away!!! Our hobby would be so much better off without them.
I had quoted Harald a price for some of his animals (this was BEFORE I had heard of the term "lowballing." I was so far off that I got a chewing out. 
