Yeah, I get that. I do. In all of my emails I ask for a rough ballpark quote or an estimate of how many hours. I realize how hard it is to do this sometimes, but you have to start somewhere.
Wild speculation: if you're at the "ballpark" stage, you probably have a very vague feature list / overall plan... I suspect if you tighten up the description and scope you'll have more luck (although given how many offers for quotes you just got, perhaps a better method is to just post on YC ;)