When paying at the Airport in Ashgabat, make sure to carry $1 bills. If you don't have the exact amount for the Visa cost ($61), they will pay you back the change in local currency exchanged at the official rate ($1 = 5,000 Manats).
At the airport, during luggage check up, you might be asked to pay $10 to facilitate your passing.
Unique Suggestions: If you wanna pass quickly, a $5 bill will be more than enough. You can also offer a few packs of cigarettes. This will make your pass much easier.
Fun Alternatives: Don't pay anything and wait for your turn in the row.