Well, I learned something new. Valve bags are real, and one company cares enough about manufacturing its valve bag fillers that it built a website on ValveBagFiller.com. Interesting.
Domains about such obscure products are tricky. Most companies that use these products have already established relationships with manufacturers and order what they need as a part of their routine. So there's not a lot of marketing competition in a lot of cases.
When marketing competition is low, it's hard to create any sense of value or urgency. But if the product is expensive to produce or something the company specializes in, they still might pay a surprising amount.
Anywhere from zero to low $x,xxx if they feel they need it. But I'd expect less than $500. And there's a good chance of zero.