Please take what I write as constructive advice (AKA - not trying to be a jerk) from someone who spends way too much time on this forum
1 - You have this posted in the wrong sub-forum (should be in wheel / tire for-sale section).
2 - New TPMS are available for $175 - $200. The OEM version (as yours appear to be) cost more, but nobody buys OEM because the exact same TPMS are available from the same manufacturer for $175 - $200.
3 - Your TPMS are used. They don't last forever (my research says 7 year life).
If you take the above into consideration, you will realize that the offer you received is actually near market price and you wouldn't need to spend your time bumping your thread for three weeks trying to get them sold.
'08 E90 M3 - Alpine White - Sold
'13 E92 M3 - Silverstone II - Sold
'13 E92 M3 - Alpine White - BBS E88, JRZ, Akrapovic, AP Racing
'04 E46 M3 - Jet Black - BBS E88, KW Clubsports, Brembo BBK, SuperSprint Exhaust, Recaro - FOR SALE