Nothing is the same price forever.
Going to be even more true in today's SaaS application world and especially if something isn't self hosted (if needing all of the server/update type of stuff), where one has to accept the price hike and doesn't really have the option of staying on the previous version until funds allow (or able to start migrating to something else).
Sometimes the move costs more than staying.
Yep, most companies do love "vendor lock-in". Have to look at whatever transitory database structure they allow for migration and how much that structure can handle with regard to what they are able to store on their end.
I would say that with any of those, going to run that risk no matter what. Sure, may go for a cheaper monthly/yearly option, but it's still going to go up at some point.
Depending on the size of the business and the needs for the CRM, could get away with less, maybe something in house. Or at the very least run an open source self-hosted CRM (if abilities (or even desire) allow for either one of these options, it's not for everyone for a variety of reasons), however, if having to go with a commercial solution, and the main reason you mentioned of price increase, that's going to be the case with any of them. Although, if I recall Shopvox is also on the more expensive side as well (but have to keep that in mind with the available feature set as well), so there is that. But just what I have to look at here, this could be an issue with any of them at any point of time, how much able to lock in depends on what the contract is, monthly, yearly, 2 yrs etc.