Solo ads prices varies a lot. You can get cheap clicks from $0.40 and "expensive" clicks for about $1.00. The price gives an indication of several things.
1. Cheap clicks are often low quality traffic that doesn't convert into sales. This is often from T2 countries. Spending $100 on cheap clicks can give you few opt ins and no sales.
2. Expensive clicks are often because the traffic is high quality from T1 countries and from fresh lists. Spending $100 on hight quality clicks gives you lots of opt ins and sales.