TBH, i never faced any spams on Steam... and seems the limit is pretty low at just $5. I think it should atleast be a full AAA game price. The limitations are really not very problematic for my use... "Browse, Buy and Play Games" lol.
Though i have tons of games on my Steam account, about 50% of them are from Humble Bundles, which wont contribute to the total spent value on steam i guess. But if it checks historical data... i had spent a LOT on Steam till about a year back... when i am just too caught up on work to play the games i buy, hence the reduced purchase.