If you sell identical or near-identical products to businesses either thru your own sales teams or partners, your sales teams generally have long-term selling relationships with their clients. Your sales team will periodically upsell, downsell, or adjust the contract in some way to promote both engagement and satisfaction with the product.
These deals run off a pricing algorithm but do use "set" pricing during the actual purchase transactions across deals. Additionally, you'll find differences in:
The consequence for late payments
Which payment methods to use
Whether the end consumer pays the bill (to Digital River)
How to handle upgrades, downgrades, and seat/quantity changes
The length and complexity of terms and billing and invoicing
A host of other smaller differences between the B2B and B2C software markets