I've contracted exclusively for investment banks in London for the past 6 years (with the exception of a brief stint at the FSA). The reason I stick with it is the exact reason you specify: the money, or more accurately for me, what the money allows me to do. The majority of the developers I work with have painted themselves into a corner with the money they've made working at banks such that they have no other option but to keep working at banks to maintain the lifestyle they've come to take for granted. The money allowed them to buy large houses, nice cars and good things but it also means they'll have to face a significant downturn in lifestyle if they ever want to move to a different sector not to mind starting a startup.

From the outset I was always conscious of not falling into the same subtle but dangerous trap. I'm not sure why, probably because I never felt 100% comfortable in a corporate environment and knew a some level that I didn't want to be trapped by it. The upshot is that we don't live a lavish lifestyle such that when the income is throttled down the adjustment isn't as severe. We don't own our house, we rent (we're actually quite nomadic so this decision is only partly financially related), no fancy car, we don't tend to spend money on fine dining and entertainment or a lot of the trappings that people often face.

This has allowed me to make choices that were right for me like taking a full 3 months off on the birth of our first child and only going back to work (for an IB I contracted with previously) for 3 days per week for the subsequent 9 months. This really allowed us the time as a family to adjust to our new circumstances. It also allowed me to experiment with a few projects that had been on my mind for a while - nothing significant just the first dip of my toes into the world of startups. Since then we've had another child - again I was able to spend a lot of time with him. I've also been able to try out a few more projects which, although not successful, have allowed me to further experiment and find my feet conceiving and building products. As a result I'm now on the brink throwing myself full time into my own bootstrapped startup which is about to open to beta.

So yes, while I agree that the money to be made from working in investment banks is great, I'd warn against getting too sucked in with the cash if you ever want to keep the door ajar for other things. Well done for making the jump into the startup world, it's a brave move I hope to join you soon. Don't pine for working at a bank, if you value creativity and and the opportunity to strike out on your own (which you clearly do), you've made the right choice whatever the outcome.