Things to consider:
1. How many "guys" (people) are you talking about when you say they are "MS guys at heart" == (amount)
2. How much will they have to learn to be as proficient at option X versus what they are good already (MSSQL) == (time)
3. How much will they be annoyed that option X "just doesn't do this the same way" == (more time wasted chatting about how dumb there boss is for making them change)
then run that through the ol' PERT analysis (shortest time + 4xlikely time + longest time) / 6, and see if that comes up to be more than your 20k initial expense..
so lets say 3 "guys"? and the project seems rather large and its doing something new, but lets guess 6 months (960hrs.. 40hrsx4x6),
lets say they on the conservative they waste 8 hrs a week learning/complaining/whatever, 10 likely and 12 if they are really mad at you for making them learn some new stuff.. ( pert says 10 after that )
so we'll say they'll blow 10 hrs a week learning the new SQL db, 240 total hrs a piece, and we'll guess there pay at $20 being non-profit and all, but probably paid more I would hope.. $4800 per person, times 3 is $14,400. so its getting in the warm zone of $20k.. would be interesting to see real numbers..