The pricing for SMS gateways will always depend on exactly what service you want. Different gateways will offer different rates for different packages - you will have to specify what services you are looking for, in order to figure out which gateway will offer the best deal for your needs. If you find a gateway based in your country, it will likely be cheaper, however, the following gateways are very reliable, offering service in most countries, and they provide detailed breakdowns for the pricing of their services:
Nexmo (www.nexmo.com)
BulkSMS (www.bulksms.com)
CM (www.smsgateway.to)