Here's my guess, but real estate attorney is definitely a must:
(1) Get quote on moving costs to business in area. If a retail business, estimate marketing costs to reach customers and local population to inform them of new location. Estimate reasonable lost business net profits for the time period (couple months?) where people are acclimating to the new location. Add this together to get one sum.
(2) Get quotes on lease to equivalent space (square footage, parking, lease conditions, location of course). If utilities and other expenses are more, make sure you add the increases (from current expenses) as well. Subtract from current monthly lease payment, and let's call this monthly operating expense differential. Then calculate the present value of this figure for the months remaining in lease, say at 3%.
(3) Add sum (1) and (2), plus attorney costs. You may be able to charge more or less depending on situation with fellow tenants, market conditions, etc.