Expense in a charger is determined by the amount of charger output power required/needed. The Thunder AC-6 I linked earlier is rated to 6S, but depending on the capacity, it will take longer than the usual 1hr lipo charge when a lipo is charged at a 1C charge rate (capacity in mah/1000 = 1C charge rate). The AC-6 is a 50watt charger and could only charge a 6S at 50watts /25.2v = ~2amps. If the lipo capacity is below 2000mah, 50watts would be plenty. If, however, your lipo capacity is more like 5000mah, then the 50watt charger would take more than 2hours. This is where you need more charger output power and that costs money unless you don't care about long charging times.

You won't find AC/DC chargers much above 100watts and those are $140-180, but they don't need a separate power supply. DC powered chargers run the entire range from 50watts to 1000watts. Provide some details on how big your 6S lipos are going to be and if you require charging at higher than 1C charge rates and we'll suggest some possible chargers.