A 25% variance in price, in most markets, isn't so crazy as to require it be some sort of terrible scam, but that doesn't mean much else. It could be the inclusion of floor plans that are carefully designed to add square footage at minimum cost and thus reduce the average cost per square foot without actually being cheaper otherwise, less insulation, thinner walls, cheap piping, minimized wiring, or they are just efficient and competitive. As you pointed out they don't have gas, so that's certainly one way you know they cut costs - no gas lines to install!
As the article from NAHB: Cost of Constructing A Home points out, though, what this figure includes can vary. Does it include the finished lot? If so then a smaller lot would mean lower square footage building price - because the land is smaller and cheaper, not the house!
Is any kind of financing quoted in the price? Compare also change-plan costs, any penalties for delays in construction, grade of materials, floor plans, customization costs, fees or premiums to pick colors/floors/counters/cabinets/fixtures, and so on. What about central cooling and heating - are they quoting an electric furnace? How does electrical heating in your area compare to the cost of gas heat? (relative pricing of electric and gas vary widely by region and climate)
In short: often square footage price isn't the whole story of what it would cost to construct a home. Ensure you are comparing everything that's important to you and you are getting a full quote, not comparing small isolate sales-pitch figures with no clear details.
If it turns out the price is 25% lower than other builders in your area and they give you what you are wanting, and you have the good sense to have a qualified home inspector and/or structural engineer inspect the home thoroughly before you take possession, then you might just have found a good builder! I'd encourage you to personally visit some of their past construction work, such as houses they build 2-10 years ago and ensure they are in the sort of condition you'd expect.