Pricing varies a lot from wholesale pricing of around 6-7c per message through to full retail pricing of 15-20c per message. Like any retail environment your price is dictated by 1. Your value add and 2. By what you think your customer will pay.
Generally clients that are price sensitive will do a lot of looking around online and quickly find services like Burst SMS and if they are willing to self serve probably take that route.
Where our resellers come into their own is with value added services. Services like phone support, account management, strategy, creative and training. If you are adding these kind of services you can resell at a much higher margin than just reselling directly.
As for keywords and numbers you can pretty much charge whatever you want. There is no real standard. We have seen keyword campaigns being charged for $1000's right down to given away as a value add. Again it really just depends on your value add and your relationship with your client.
We have found that reselling SMS is a fairly hands on process when getting a client initially. You will need to speak with them, understand their situation and offer them a solution. Once that is done they will pretty much take care of themselves.
If you are not sure and are not value adding and just want to resell directly just start out adding 100%. This will give you plenty of room for negotiation. Remember once you set your price it is easy to go down but almost impossible to go up.