It depends greatly on the industry. If it is seen as a B2B convenience by your customers, especially if you don't see any real value in using it to reduce churn, then pricing should remain the same so that monthly clients don't feel like they're being screwed. If you're trying to push people towards it for your own convenience because of cashflow or other issues, I'd say that the "common" SaaS practice seems to be offering two months free per year (so it would go down to $2,499/yr. Anything less than that and you're asking your customers to pre-fund you for no benefit to themselves, which won't work very well.