The other thing is that building your own greenhouse kit offer your more flexibility. You have an opportunity to choose the materials you want to use. For building your own mini greenhouse, it is highly recommended to choose copper since it is more durable compared to the majority of other materials that are traditionally used to build mini greenhouses. For example, you can choose the materials you are going to use as a cover. When you choose to build your own mini greenhouse kit instead of buying one, you are able to use something suitable for the needs of the plants you are going to grow. For instance, plastic is better to b used in early fall and spring while shade cloth is better to be used during the summer because it has an ability to maintain cooler temperature.
And with the readymade mini greenhouse kits, you do not have such options.
In addition, learning how to build a mini greenhouse is less expensive compared to purchasing these mini greenhouse kits. Probably there are some scraps around your house that could be used to build a mini greenhouse. All you have to do is to scour whatever you store your unused resourced and you could be surprised to see that there are a lot of different things for you to use for your hobby greenhouses.
However, what you will need are some additional suppliers and a greenhouse plan that you can follow.