At the time of the celebration, the market in town was literally swarm with stalls and any sort of good could be easily purchased. Due to the importance of the celebration, and the fact that most goods were paid on the occasion of the festival, the Sardinian expression “a pagai a Santu Luxori!”, meaning that something is to be paid in the future (literally during the celebration), entered the common idiom.
The market was crowded with vendors selling goods at the time of the celebration, and because of the importance of the event and the fact that most purchases were made on the festival day, the Sardinian expression "a pagai a Santu Luxori!" entered common idiom.