פירוש על קידושין 57:1

This illustrates the second half of the mishnah. The Temple acquires things when someone simply says they belong to the Temple. Ordinary people transfer objects by physically transferring them.

The ordinary person described here is acquiring something from the Temple. He pulls it to himself, but has not yet given the money. Then the price goes up. He must pay the higher value. This would not be true if he were acquiring something from another person. In that case, once he pulled the item to himself, it would be his.