Depending on the space that you have available you can build your own Indoor Putting Green for around $200 to $400 depending on the size and also the materials used.
The Matting
The most important factor apart from it being structurally sound is the matting you select for the putting surface. True, you can buy synthetic grass for a hardware outlet or landscape supplier however most are made from a coarse pile and when used for putting do not give you a realistic ball roll. This is the most crucial element to having an Indoor Putting Green to practice on. If you are practicing on a poor surface your results will be poor.
We have attached a couple of images of a Putting Lane we built as an exercise a couple of months ago.