Another option you may want to consider is to create 2 different brands. One for large customers and one for smaller ones. It could be 2 different websites but

Another option you may want to consider is to create 2 different brands. One for large customers and one for smaller ones. It could be 2 different websites but with the same backend system. Usually large customers don't like to use the same tools as smaller ones, and smaller ones may feel your system is too "high end" if they'll see an option with a 10K pricing tag. You can create a smaller brand with only email support and charge less.