The Visa cost stays at 50 USD. Nationals of just 40 countries are eligible for the visa, these are mostly western countries. Nationals of most neighboring countries, on the other hand, can visit these countries visa-free.
Univisa will be valid for 30 days and allows multiple crossings between the two countries (limited by passport pages as it gets stamped at every crossing!). If re-entering from a third country, a new visa has to be obtained, even if the previous visa is still valid. The only exception is a day trip to Botswana (most likely a safari to Chobe National Park).
The visa can be obtained on arrival at these airports: Lusaka, Livingstone, Victoria Falls and Harare. It is also issued at the two Kazungula border posts bordering Botswana with Zambia and Zimbabwe, respectively. Unfortunately, those arriving by land from other countries, like South Africa, Namibia, Mozambique, Malawi or Tanzania still cannot obtain the visa.