This can be a longshot....but consider making a "travel buddy personals ad"! You can post it here, in the Travel Partners wanted section. You could also try craigslist.com in the strictly platonic section.
Four years ago I was living in France and posted on the Rick Steves Travel Partners Wanted board. I invited people passing through Paris to meet and spend time with me. A guy answered my ad and we met up a few times in Paris. One time we shared a hotel room. We became friends and although he lives in Missouri and I live in Florida, we've kept in touch. Last December we spent 3 weeks traveling around Italy and this December we're going to Disney World for a week!
But to really answer your question:
I think it is a lot cheaper to travel independently than on a commercial tour. Really, the only thing that costs more as a solo traveler is lodging.
Hostels seem to be getting more all ages friendly, so you may want to consider that. Even though I'm 24, I was never in to the drinking and party scene, so for a long time I avoided hostels. But I've found that if you do research you can find some hostels on the quieter side. Plus, a lot are offering private rooms (with or without bathrooms) for a lot cheaper than a single room in a traditional hotel. Another bonus with a private room at a hostel is that you usually have access to kitchen facilities!
Another option you could look in to is Couchsurfing. Basically you offer up your home for travelers to stay in free of charge, and you can request to stay at other peoples homes. It's like a global house guest exchange. The mission statement is "CouchSurfing seeks to internationally network people and places, create educational exchanges, raise collective consciousness, spread tolerance, and facilitate cultural understanding".
Check out the website: www.couchsurfing.org
Happy Solo Traveling!