To sell a product, that takes months to integrate, and change the pricing structure completely without warning is basically insane business practice. At LEAST provide a per user rate for the little guy, and change the t+c to assure customers there will be fair warning and 'not more than x% per annum increase'. A price change for a product like that should be given 6months notice and an incentive to grow into the new structure (ie grow to over 100 customers before we change the price and you'll get 10% off for another 6months.