SSL certificates can be quite pricey. If you are running a website and do not have much of a budget, then you may consider that it is something that you can easily do without. However, it is something that you should consider hard.
If you need a secure site in order to keep your customers happy, then you should get a certificate. Otherwise you will need to consider whether it is something that you think is necessary or not. If you are having data transferred across the site, then you will need to consider it.
There are different types of SSL certificates though and they provide different levels of security. It is worth learning more about the types and comparing the costs. This will allow you to calculate which of them will be the best one for you to use. You may find that a fairly cheap one will give all of the cover that you need or that you need to pay out more money.
Obviously the choice is yours and it could be constrained by your budget. However, consider the effect on your business if you do not have one and whether you need to find the money somehow so that you can get a more expensive one. You may lose so much business as a result of not having one, that you may regret it. If you pay for a cheap one, you could find that it does not give you what you need and you would have been no better off not getting one at all, with regards to the customers reaction to it.
It is therefore a very important decision. Obviously you want value for money and you do not have to pay out more than necessary. However, if you do not pay enough, then you may lose out with regards to sales.