E-2 sets no fixed dollar minimum. The investment must be substantial relative to the total cost of buying the business, and a purchase of an existing campground in full is ordinarily proportionate. Government fees are separate and small by comparison.
Substantial is a proportion, not a threshold
Hypothetical example: a Frontenac Islands couple negotiate a price for the campground that includes land, cabins, equipment and goodwill, and ask what portion must be their own money for the investment to be substantial. The test is proportional: the amount invested is compared to the cost of purchasing or establishing the enterprise, and a higher proportion is expected for a lower-cost business. Buying an operating campground outright, with most of the price paid from their own funds and the balance from a loan secured on Canadian assets they still own, is ordinarily substantial.
A loan secured on the campground itself does not count toward the investment because those funds are not at the investors' risk. The consular fee for the E-2 visa is set by the Department of State, and a change of status inside the United States would involve a USCIS fee under Form G-1055, but neither approaches the real cost, which is the working capital a seasonal business needs to reach its first May.