For a single-entry/day admission?--Absolutely not, and I don't see how they can justify it. If anything, there should be discounted prices for travelers in order to attract more tourism. For example, as inflated as prices are for tourist attractions in Niagara Falls, there are certain discount packages available only to non-residents. (Still expensive, of course, but it's something.) Granted, the Biodome doesn't attract the same level of traffic as the Falls...all the greater reason for them to show their appreciation to their out-of-town patrons. If they want to have a season's pass/multiple entry pass at a discounted price, that makes sense in order to cater to local residents who may want to come more frequently. But not a standard admission price.
Some attractions I've had the pleasure of visiting are LaRonde, Vancouver Aquarium, Ontario Science Centre, various museums country-wide, Canada's Wonderland, Marineland, practically everything there is to do and see in Niagara Falls and Toronto, tons of outdoor physical activities across the country (i.e. skiing/boarding) and that's just getting started. None of these locations charge a separate price for non-residents of the province. (At least not the ones I visited...)