I am thinking of going BOS-LIS in September. Does anyone know about air fare from the USA to LIS? It seems if you stay 7 nights/days it is less expensive. Lowest I found was around $650 on SN. Most are around $1,000-$1,200. I would like to stay maybe 4 to 7 days. Is it less expensive to go into a different city in Europe, and then fly to LIS?