Our development concept is using agile test-driven development to quickly deliver tangible results which lets the customer drive the path forward. We use eXtreme Programming and SCRUM technologies. We use test-driven development with proven best of breed practices in Python development. We have issue tracking that closely involves the customer in the project. But flexibility is our keyword, and we are able to adapt to customer requirements.
Agile development is based on flexibility and adaptability. It will give you what you need, even when you aren't entirely sure what your needs are from the outset. Since you only pay exactly for what you want agile development is cheaper than the traditional fixed price development where you first pay for development of features and then pay to get them changed or even removed when they didn't work exactly as you expected.
The Fixed Price Phase
The most common worry with agile development is that there is no budget, so the customer has no guarantee that he will get anything useful within what he can afford. Therefore the most common practice with us is that the customer lists the requirements for basic functionality, and we offer a fixed price starter project that is guaranteed to deliver what the customer specified. The requirements for the fixed price phase are all about functionality, specified in a high level to give flexible implementation options. At the end you will have an application that does what you need. But typically at this phase you discover that this is not exactly what you want. This is an effect of all development according to the old "waterfall" methodology, and usually the result of that is another expensive project to get what you want. At which point you discover that it wasn't exactly right either. To solve this, agile development methodologies was developed.
The Agile Phase
For the agile phase we will implement any changes desired on a change-by-change basis, in close cooperation with the customer. This will deliver to you exactly what you need for the smallest possible cost, and the fastest possible time. Although we can do both fixed price and agile development, the combination of a fixed price starter phase and an agile phase is the most popular as it delivers a combination of flexibility and guarantees that suits most customers.