Hostels and backpackers lodges are not easy to find in Madagascar, with the closest approximation being hotels at the cheap end. And while these can sometimes bear a strong resemblance to dedicated fleshpots, but that is cheap accommodation, particularly in Antanànarìvo. For between US$15 to US$20 there are a handful of small hotels in the mid to lower range that are somewhat better, but as a rule of thumb cheap hotels in the capital are about as close as you will be able to come to budget accommodation.
Outside the capital the situation is not that different, although prices tend to be cheaper and standards a little more varied. For what you might expect to pay for a room at a backpackers lodge in South Africa, Zimbabwe or Namibia, you will find a comparable hotel room, perhaps even with en-suite ablutions and air-con. All these establishments have a distinctly local flavour, with sometimes pleasant shades of the old francophone association very visible.
In conclusion, therefore, it is probably fair to say that rough travel in Madagascar is as rough as luxury travel in the same country is luxurious. Possibly the mass market has less appeal in Madagascar than wealthy South Africans and Europeans taking up rooms on the island and beach resorts which is where it is really at in Madagascar. If there is any comfort to be drawn from roughing it in the fleshpots and bordellos of the countryside it is that at least the you will see much more of Madagascar than they, who spend their fortnight encapsulated in tour busses, and billeted under thatch and mosquito netting with the soft lap of the Indian Ocean to soothe away their many regrets.