Byetta is expensive. If you can't pay for it yourself, you have several options.
1. Find a clinical study that uses Byetta. Joslin Diabetes Center is sponsoring several of these. If you're not close to Joslin, Center Watch also keeps track of trials throughout the country.
2. If your income is low, you can write to the drug company and explain that you can't afford their medication. Sometimes they'll give it to you free. It involves a lot of paperwork, as you have to reapply every few months, but it might be worth it.