I can maybe clarify some stuff as I and a few other contributors on here were involved as a sounding board by Leeann and Derek Weir.
From the club website in 2013: https://www.motherwellfc.co.uk/2013/03/19/well-society-sign-up-night/
Junior Steel Membership – £25 (for juveniles under 15)
Steel Membership – £300
Claret Membership – £,1000
Amber Membership – £5,000
1886 Membership – £25,000
The annual fee was to keep your benefits alive (which at the time were pretty substantial), from memory Amber benefits for an annual renewal fee of £1,000 maybe? you got stuff totalling way more than annual contribution. Not paying the annual fee did NOT affect your voting rights, just access to the benefits as per your tier.
The £300 barrier to entry was something they were aware of at the time and DD's were floated at launch but there were fears it had financial compliance issues with the WS being a provident society. A few years down the line Hearts blazed that trail and we embraced it but more as a means to appeal to a wider audience to attain £300 steel membership (and beyond if you wished) in easier to swallow chunks. It was not sold as a universal adoption by all members, more it would be nice if you did.
I can recall from when £5 was deposited new members post 2015 got their membership pack and voting rights which caused some consternation at the time, over them getting to £300 deposited, maybe it was part of the sales tool to boost membership.