Prices for expert advisors are very different. At the very beginning, I used gps forex, which cost 150 bucks. Profit was about 5%. But this figure varies greatly depending on the currency used, the economic situation, and the quality of adjustment to the current situation. You need to be in touch with the developer's support, you also need to constantly simulate various market behaviors, and so on.
I think that you will not regret if you open account here. I am scalping with this broker for almost a year. It is stp ecn broker, so there is absolutely no issues with deal executions. At least I didn’t experienced any. Through my ea, I sometimes make few deals within a minute, and didn’t have any delays neither have experienced that my deals were not executed.
There are no spreads on ecn account. Commission is $7 for full lot. You can also trade here micro lot. Withdrawal of funds is without commission, but I always pay banks commission, since I am making wire transfer.