What's a reasonable price for a head gasket repair and new radiator?

What is your question?

My car was running fine but the window motor was broken or so I thought. I got a rental before they figured out I left the lock button on, so to make it worth my while since I had already rented a car I did the "60K level service" based on their rec, along with a rear break adjustment (even though I had the front breaks done 2 weeks previous and you think they would have adjusted them then!)...done at 85K miles by the shop less than a month ago. It other words after that my car was in tip top shape. I asked them about trading it in and they said, no with the work you just did it's going to run forever. But...I swear they didn't check the fluids. The AC stopped working, then fluid light and engine light came on. It was at night and I saw no coolant in the over-fill compartment and no fluid in the wiper compartment so I added water there and kept checking it along with oil levels. I barely drove this (1-2x a week) and was out of town a week where it sat in an underground garage. I was going to drive it by the shop to have them check on why the AC was having issues as well as the lights (fluid and engine) coming on when my engine cut out on the freeway, and it being 103 degrees outside.... A burning smell and flopping of a fan noise and I pulled over. I had it towed to the shop and they said oh, "we didn't check the front (meaning radiator and wiper fluid)" they were apologetic and willing to pay for a rental. However, now that the damage is beyond coolant they are blaming this on a faulty after market radiator. But it seems to me a seam busted on the bottom of the radiator is more likely caused by high electrolysis explosion from the busted gasket head which was also caused by old/no fluids that obviously weren't filled. Now they say they were filled and are quoting me $1300 at a minimum range where friends have said the $750 range would be the most to look out for. Anyway it seems to me they are at least partially responsible and partially ripping me off and now trying to scoot responsibility. Plus it seems impossible for it to go through enough coolant in less than 3 weeks to make the fluid light go on and if the radiator had busted at the seam that caused the lack of fluids my car would have quit functioning a lot sooner and I would have heard something since they call it a sudden bust senario. So what's a reasonable price for all this since want to machining the heads "just to be sure" and said they are "only charging me $300-400 in labor." Radiator, hoses and gasket heads... The place is family run and the tech guy is a retired Toyota guy but the owner er quoter hasn't performed this type of work. And are they responsible or not?