We just had our asbestos tiles removed - it was about $3300 for maybe 1100 square feet. Our mastic didn't have asbestos, but it wouldn't have been much more to remove it too. Most people thought we were crazy to not just encapsulate, and I agree.
Pretty much, they would coat the tiles with a sealant, then put down flooring on top. That depends on the type of flooring, really. We're seeing prices ~$6-8/square foot for cheapish grade flooring and installation - vinyl and laminates.