Prosaic, you are correct in that from a rock-bottom minimum per month cost with phone number, Page Plus is the cheapest you can get at $2.50/month without sink-holing a giant wad of money up front or going the ARN outbound only emergency phone approach. There is a 50¢/month service fee to keep the line active, which effectively gives you 80 available minutes per month at that price, which is a reasonably usable quantity. The only real downside to this is the Verizon CDMA lock-in with the handset along with any added complexity if handset replacement is necessary, and the now pending acquisition of Page Plus by America Movil which has a history of difficult customer support practices and eliminating cheaper plan options on their acquisition brands.
Seattlecyclone, your math is only accurate from a surface approach with T-Mobile being the cheapest as has been pointed out (PP holds that title at $30/year with 10¢/minute billing at that price even with the monthly service fees). Going the $10/90 days approach until you hit Gold Rewards status means you're locked in to paying 33¢/minute for the first 2.5 years of service... or basically $100 for roughly 300 minutes. That's 10 minutes of talk time a month for the money. If you can't see yourself even using that much, you officially don't need a cellphone at all (even if 20 minutes a month itself should be worthy of debate).
Now it's true that if you start out of the gate with the $100/365 day service card that immediately puts you into Gold Rewards status where the $10/30 minute card gives you an additional year of airtime, but at 250 minutes a year usage levels, you're locked into T-Mobile for the next four years to get all your money back out without increasing usage levels substantially. Additionally, there's been increasingly lousy customer service quality and "billing error" issues in T-Mobile's Prepaid division where people's balances are slowly evaporating on them without use. I'd heard scuttlebutt about it online a good number of times and dismissed it as user error, but then someone I knew started having the problem.
So technically, yes, you're effectively using $25/year for service usage (technically closer to $32.50 in actual cost if you count the $30 needed to finish out the $100 balance at current usage levels), but realistically and on the books, you paid $100 for the service up front, and have to commit to staying with T-Mobile through thick and thin and keep spending $10 a year for three more years to use up your remaining invested airtime, then wash-rinse-repeat with the $100+$10+$10+$10 approach for another four years to get per minute rates approaching anywhere near reasonable and competitive for long-airtime service.
A far better option for that level of usage would be Airvoice's Pay as You Go plan, as you'd effectively get that same per minute/text rate as T-Mo at $10 a pop each 90 days for that 250 minutes a year usage level without the huge outlay up front. There's a $1/month maintenance fee, but that leaves 70 minutes for usage every 90 days plus rollover, or 23 average minutes a month (the available minute/month math works out roughly the same as your $130/1090 minute/4 year approach). Airvoice's customer support is pretty solid, too, and you'd get a bigger GSM footprint on service with AT&T's network which may or may not matter, and only costs an extra $7.50 a year, or on average 63¢ a month. It's not to say that one can't take the T-Mobile prepaid approach (and if it's working for you for the time, stick with it), but there are much better options for the money in prepaid that still provides you the freedom to walk away to a better deal without leaving too much on the table depending on usage change habits or to a less abusive provider if need be. This is why I don't particularly recommend or point out that route even before the problems with T-Mo's prepaid division cropped up.
Let us be frugal and wise with our investments, not cheap. :)