Although it is possible to arrange your own Russian visa, most travelers choose to hire a visa service to do the work. Russian consulates have many options for visa processing, from a regular 2-week (cheapest) processing, to a very fast (and terribly expensive) same-day processing. If you live in a city with a Russian consulate, you may save some money by going and applying on your own. Beware, that most Russian consulates only accept paperwork early in the morning.
But if you want to make sure you get your visa on time and without losing any sleep over it, hiring an experienced visa-expediting agency is the way to go. Since Russian visa also involves getting a Russian invitation, you want to deal only with those agencies that can assist you in both. Invitations can cost anything up to and beyond $500, depending on the type and the speed of service. For an extra $30-$70, agencies will offer full processing (invitation, taking visa to a consulate and sending it back to you). The best services will take care of registering the visa when you arrive in Russia. Given that each Russian consulate and embassy has different tastes and temperaments, it's usually best to have somebody who knows the ropes do the dirty work.
But if you want to make sure you get your visa on time and without losing any sleep over it, hiring an experienced visa-expediting agency is the way to go. Since Russian visa also involves getting a Russian invitation, you want to deal only with those agencies that can assist you in both. Invitations can cost anything up to and beyond $500, depending on the type and the speed of service. For an extra $30-$70, agencies will offer full processing (invitation, taking visa to a consulate and sending it back to you). The best services will take care of registering the visa when you arrive in Russia. Given that each Russian consulate and embassy has different tastes and temperaments, it's usually best to have somebody who knows the ropes do the dirty work.