Russia raised the price of its visas to $125, in retaliation to the American Embassy charging Russians who want to apply for a visa to visit the States. And if you need it faster than 6 weeks, you'll have to pay extra. Assuming that it'll cost you $250 a couple just to get off the ship to have a look around, you might as well pay a tour guide the money and avoid the visa. Better yet - team up with four other passengers and share the cost of a Red October tour guide and van driver. Here's a tip - bring a couple of colorful decals to slap on the exterior your van - all the vans over there look alike, and it was a game to try to spot our van among the dozens of white vans waiting in the parking lots.
Also, make sure your passport is up to date - there are inspectors at St Pete who will give you and your passport a serious going-over before letting you off and back on the ship.