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.
'13 SSII M3 Coupe - KW Clubsport 3-way, Akrapovic Evolution, ESS Tune, StopTech Trophy, IND Euro Front Bumper and Gloss Black Mirror Covers, TMS Studs/Lugs, BMW Performance Carbon Fiber Spoiler/Interior Trim/Center Console, BMW Edition Grills/Gills, BMWPedals Extended DCT Paddles, Advan TC3 18x9.5 & 18x10.5 - Hankook RS3 (Track), HRE R40 - 18x10 & 18x11 - Michelin PSS (Street)