Yes, crypt surgery can be quite expensive compared to regular gelding surgery; sometimes as much as 5x more than regular surgery (possibly more than that depending on the region and vet).
Sometimes, upon sedation, they pop to the surface and regular gelding can be performed. Many minis don't drop until 3-4 years old, so if you have room to keep him separate from mares, give him a bit more time (at the very least til next spring). Have you palpated the region? Or, just looked and don't see?