The only reason to need a TPMS kit is if the shop has a track record of breaking TPMS sensors. That should be enough of a reason to find another shop. Ask the shop if they will give you an 80% discount on the nitrogen fill.
2013 328i MSport
2012 X5 50i (returned due to PCS move)
2008 M5 (traded for X5)
2004 330ix (former winter beater)
2003 M5 (traded with 103k, still working fine)