At any rate we're talking about toast here and an oven broiler only has one setting (usually): all the way on, so you're using as much energy as it takes to brown a steak just to crisp up a bit of bread.

It's not really about heating up the air, anyways, toasters and broilers mostly directly heat things. A toaster (or toaster oven or countertop convection) just has the elements closer so can direct more energy into the bread and less to.. everything else.

Ovens I've used take roughly 15minutes to warm to 400F (200C), regardless of if they are electric or gas.

That said, you can buy a toaster oven for $30 from Walmart, and that cost covers the energy, material, transportation, and labour, plus markups at each stage. If you assume a $0.10/kWh energy cost, you might have at absolute most 100kWh of energy used in manufacture. That puts the oven/toasteroven breakeven point from an energy perspective at no more than about 60 hours of heating element usage.