Buying links from exchanges is not link building. Unlike buying external data, building up links is a routine and time-consuming process, since donors are selected manually. Link building on non-spam, reputable sites does not lead to search engine sanctions because it mimics natural business mentions. Perpetual link exchanges are special platforms on which you can place a perpetual link to the promoted site. Exchanges can make it easier for SEO-optimizers who buy them automatically according to the necessary criteria, at the same time, placing on bad donors can negatively affect your domain. The price of perpetual links varies depending on various factors: portal rating, traffic, topics, content uniqueness, location area, age and domain level, etc. It is important to pre-budget funds for website promotion through link building.