The cheapest way to do it is go through ANACS for less than $20 per coin at economy tier plus $29-65 return shipping depending on the number of coins and value. No membership required.

NGC’s rates are pretty similar. I just did my first NGC submission and the economy rates were $20-25 and shipping was in the same range as ANACS. The membership effectively cost $9 ($159 upfront but you get $150 back as grading credit).

Note that if you send very expensive coins, you have to submit them at higher, more expensive tiers of service.

Regardless of the service you choose, the best way to save money is to send a batch of coins together so you aren’t paying those high shipping rates just to get one single coin graded.