Lowes has Whirlpool 50-Gallon 6-Year Tall Natural Gas Water Heater List price of $525 which is the standard price a water heater with these specs. Equivalent Rheem is listed at $607 at Home Depot

• 10-15% off through Jan 18th 2017 on select appliances at Lowes.com = -$52.50
• Buy 2 get 10% off. Use a filler item such as Shop Vac 5 Gal Filter (14.99) or Other Items and return after purchase. = -$47.25
• 10% off "Online" Coupon Code can be had for $1 on ebay = -$42.52
• Total 382.73

Keep in mind water heaters need replacing anywhere from 6 years old and up.