There are four options to transport bikes home after the tour:
1) Partially disassemble bike, pack in a bike box, and ship via UPS or FEDEX ground
This is a practical solution where a local bike shop does the disassembly, packing and shipping. The touring biker rides the bike to the chosen bike shop and drops it off. The biker should do a bit of research on nearby bike shops to get an idea on costs charged by the shop to pack and ship. The prices can vary greatly, so getting estimates from the bike shop are in order. Recommendations from others or online reviews such as from Yelp.com may be helpful.
From, my experience, FEDEX provides the best ground shipping rates. But both FEDEX and UPS have online calculators, so check it for your particular situation (shipping distance, weight, box size).
There is an adder for over-sized bike boxes. Try to keep the girth of the box less than 130 inches for the best prices. The girth is the total of the length plus the distance around the width and height. A box 50" long by 26" high by 10" deep would have a girth of 50+(2*26)+(2*10) = 122" and would be less than the 130" limit. Boxes bigger than the 130 inch girth will cost significantly more to ship.
2) Partially disassemble bike, pack in a bike box, and check in as baggage with airline
Taking a bike home in packed in a bike box and checking it in as normal luggage may be the cheapest solution if the weight is less than 50lbs. but perhaps not the most convenient. Alaska Airlines, for example, charges $20.00 if under 50 lbs. for domestic travel for regular passengers (possibly free with mileage program members). However, there is a logistical and inconvenience factor in lugging a big bike box to the airport, such as the need for special taxis which can handle oversized luggage, or the need for transport assistance in carrying the box to the airline check-in counter.
For international travelers, however, this approach may be the most viable and practical option.
Again having a bike shop do the disassemnly and packing is a practical solution. The same comments apply as in case (1) regarding finding a good bike shop.
3) Take on AMTRAK, if returning by train
If traveling home by train, Amtrak offers several options for transporting the bike. In most cases, the bike will be checked in as luggage for $10.00. The bike must be in a box (yours or Amtrack will supply a box for $15.00). Bicycles must be partially disassembled in order to fit in an Amtrak bicycle box. Loosen and turn the handlebars sideways, and remove the pedals. Amtrak does not supply tools for disassembling. I would have a bike shop use a special tool to loosen the pedal nuts (usually they are very tight) and use a simple wrench to remove the pedals when packing the bike at the train station using a purchased bike box. Bicycles may be checked on Amtrak between all cities where checked baggage is offered but not all trains or locations are equipped to handle checked baggage.
Full-size bicycles may be carried on certain trains with designated "walk-on bicycle service." Bicycles must be stowed in the designated space within the body of the car. Passengers utilizing the walk-on bicycle service, where bikes are carried on select trains by the passenger and stored in designated areas, must be able to fully handle their bicycle, and be able to lift their bicycle to shoulder height. Passengers are responsible for stowage and security of bicycles. This option is usually available on shorter distances.
Amtrak fares may cost more than discounted airline fares and take significantly longer. However, for shorter or even moderate distances, I like the Amtrak option because you can ride to the Amtrak station, buy a ticket, put the bike in an Amtrak box (or just hang it up fully assembled where walk-on service is available), and enjoy the train ride.
Check for details with Amtrak and if there is a nearby station.
4) Rent a car
A one-way car rental to return home has the advantage of transporting you and the bike home at the same time with the most flexibility. Only minor bike disassembly is required (wheels off, twist handlebar). This option is a very good option for shorter or moderate distances.