Believe it or not, trekking in Nepal is actually really inexpensive compared to trekking and traveling in most other countries. You can find plenty of 2–3 week treks for around $1,000/pax, which covers accommodation, food, guides, porters, etc. Everest Base Camp treks are very popular, so a lot of tour companies run them, and you can shop around for the best deal. Since the earthquake last year, tourism has been down in Nepal, and tour companies (many of which are locally owned and operated) are eager for business.
If you’re looking for an alternative to the EBC trek, I recommend Manaslu Circuit. Less crowded, less traveled, and huge variety to the scenery, climate, and villages we passed! I was in Nepal for nearly a month in 2013, and the whole trip (trek + Kathmandu + Chitwan park) cost less than $2,800 - and the flights were more than half the expense.