So, you are telling me $3750 for exchange services PER YEAR for 25 employees is somehow better that what was being offered in Small Business Server 2011 Standard (75 users) which is $739.99 on Amazon right now? You could easily put this on server hardware for <$3000. Let's say it even costs you another $3000 to an IT consultant to setup. In 5 years time you are going to pay MS $18750 for exchange services, your server will only have cost you ~$7000. You can't argue paying for support would cost more with your own server, because you still need an IT consultant for other issues and even to possibly maintain a small file server (not to mention paying one for the initial setup or migration to hosted exchange services) if you have hosted exchange services. I doubt it would cost $11000 more in IT consulting services and office desktop applications for 25 users.
Office 365 is all about a steady stream of revenue for Microsoft, not about giving small businesses what they need and saving them money.
If all you need are Exchange services, then its only $1200 per year for 25 employees. Small businesses would rather pay this than having full time IT staff. They also won't have to pay for any support on their servers or have to worry about downtime as much. When the next version of Exchange server comes out, you'll automatically be upgraded. Over a 5 year span, you're paying $6000. Compare that to 5 years of Exchange licensing (25cals), server hardware and support, backups etc. Most small businesses under 25 employees don't have their own IT staff anyways, so this is a reasonable option.