Question about new steam boiler..?

My parents are having their steam boiler replaced, because there is a leak (steam). Their house was built in 1914. I don't know anything about boilers, and neither do they. They were quoted $7,5000 for a new steam boiler. Does that sound right? They need to heat approximately 2,200 sq ft. The BPU (or is it BTU??) is 100,000 or 200,000. Like I said, our knowledge is extremely limited. The fuel type is natural gas. If anyone could let me know what's to be expected, and whether or not my parents are getting screwed, I would really appreciate it. Thanks for your time!