Additional costs can really build up, especially if you encounter any delays. Just scraping over the funding line could be a worst case scenario.
If you’ve run multiple campaigns and are 100% confident of your numbers or if you have reasonable levels of finance in place before the campaign starts then this one might not apply, but for first time crowd funders there often comes a point in your campaign where an extra boost will just get you funded and it’s incredibly tempting to do it. So what’s the problem? Well for a start, you’ve probably priced your Kickstarter at a “worst case” level, with the exact funds you think you need to deliver the project. Lower goals fund faster so it’s rare for a project owner to set the goal higher than they believe they need. Everyone expects their project to be a success and nobody wants to be seen as a failure.
So what happens when you crawl past your goal and end up funded by £5? Well first, you’re going to lose a percentage of that money to failed credit card changes. 5% of payments failing isn’t an unrealistic scenario in my experience, so now you’ve got a funded project and 5% less money than you expected.
Then costs start to mount in other places you haven’t expected. A few people change their mind and ask for their money back. You aren’t required to give it to them, but it’s not worth the argument in the comments for the sake of a few pounds, so you refund them. Then a production sample of one of the products has a slight flaw. Maybe it’s the fault of the factory, maybe it’s something you missed earlier. Either way it has to be fixed and so best case you’re delayed, worst case your factory asks for a bit more money. The delay annoys a few people who ask for a refund.
Depending on the country you’re in, taxes can also be a pain. Even if you expect to get tax back (you’re VAT registered in the EU, for example), there is still likely to be a point where you’ve paid some tax and are waiting to get it back. That’s fine if you funded comfortably, but if your cashflow was already tight it can be a killer.
That’s just a few things that can go wrong, there are plenty more and it’s almost impossible to plan for them all. So what is a better solution? Come in just under your goal and you’ve got an opportunity to fix whatever the problem was. If you didn’t fly past your goal you either had a product people didn’t want, a marketing campaign that didn’t resonate with them, or a goal that was unreasonable. Find out what it was, fix it, then come back with a new campaign. If your original backers liked your product you’ll be able to get most of them back, and hopefully your updated campaign will bring in a whole new audience.